(Mark One)

þ		ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 [NO FEE REQUIRED]

o		TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 [NO FEE REQUIRED]

A.

Full title of the plan and address of the plan, if different from that of the issuer named below:

B.

Name of issuer of the securities held pursuant to the plan and the address of its principal executive offices:

225 West Station Square Drive

Suite 700

Pittsburgh, Pennsylvania 15219-1122

 

 

WESCO Distribution, Inc.
Retirement Savings Plan
Index

		Page(s)
Report of Independent Registered Public Accounting Firm			1
Financial Statements
Statements of Net Assets Available for Benefits as of December 29, 2010 and 2009			2
Statements of Changes in Net Assets Available for Benefits for the fiscal years ended December 29, 2010 and 2009			3
Notes to Financial Statements			4-15
Supplemental Schedule
Schedule H, line 4(i) — Schedule of Assets (Held at End of Year) as of December 29, 2010			16-43
Exhibit 23.1 Consent of Independent Registered Public Accounting Firm			44
EX-23.1

Report of Independent Registered Public Accounting Firm

To the Participants and Administrator of the
WESCO Distribution, Inc. Retirement Savings Plan
Pittsburgh, Pennsylvania

     We have audited the accompanying statements of net assets available for benefits of the WESCO Distribution, Inc. Retirement Savings Plan (the Plan) as of December 29, 2010 and 2009, and the related statements of changes in net assets available for benefits for the years then ended. These financial statements are the responsibility of the Plan’s management. Our responsibility is to express an opinion on these financial statements based on our audits.

     We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States of America). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements. An audit also includes assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

     In our opinion, the financial statements referred to above present fairly, in all material respects, the net assets available for benefits of the Plan as of December 29, 2010 and 2009, and the changes in net assets available for benefits for the years then ended, in conformity with accounting principles generally accepted in the United States of America.

     Our audits were performed for the purpose of forming an opinion on the basic financial statements taken as a whole. The supplemental schedule of assets (held at end of year) is presented for the purpose of additional analysis and is not a required part of the basic financial statements but is supplementary information required by the Department of Labor’s Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. This supplemental schedule is the responsibility of the Plan’s management. The supplemental schedule has been subjected to the auditing procedures applied in the audit of the basic financial statements and, in our opinion, is fairly stated in all material respects in relation to the basic financial statements taken as a whole.

/s/ Alpern Rosenthal

Pittsburgh, Pennsylvania
June 27, 2011

WESCO Distribution, Inc.
Retirement Savings Plan

Statements of Net Assets Available for Benefits
December 29, 2010 and 2009

		2010				2009
Investments at fair value (Notes 2, 4, and 7)
Shares of registered investment companies		$	206,330,334			$	177,568,193
Common collective trusts			22,094,976				20,074,381
Stock funds and self-directed accounts			23,263,414				15,724,184
Stable Value Fund			112,092,798				109,219,294
RAFI Enhanced Large Company Fund			23,152,545				20,946,580
			386,934,067				343,532,632
Receivables
Employee contributions			—				746,094
Employer discretionary contribution			13,335,799				—
Accrued interest			21,714				20,496
Promissory notes from participants (Note 5)			11,111,960				9,154,053
Net assets available for benefits at fair value			411,403,540				353,453,275
Adjustment from fair value to contract value for interest in the Stable Value Fund relating to fully benefit-responsive contracts (Note 7)			(5,836,194	)			(4,410,440	)
Net assets available for benefits		$	405,567,346			$	349,042,835

The accompanying notes are an integral part of these financial statements.

WESCO Distribution, Inc.
Retirement Savings Plan

Statements of Changes in Net Assets Available for Benefits
Fiscal Years Ended December 29, 2010 and 2009

		2010				2009
Additions
Employee contributions		$	21,050,278			$	20,913,407
Employee rollovers			823,825				1,169,935
Employer contributions (including discretionary contributions)			19,843,174				4,022,410
Net appreciation from shares of registered investment companies			24,621,547				45,493,206
Net appreciation from common collective trusts			2,311,901				4,284,853
Net appreciation from stock funds and self-directed accounts			8,188,226				4,899,661
Net appreciation from the Stable Value Fund			4,850,771				5,105,486
Net appreciation from the RAFI Enhanced Large Company Fund			3,405,912				5,372,105
Interest and dividend income			4,550,634				4,237,192
Total additions			89,646,268				95,498,255
Deductions
Distributions to withdrawing participants			32,381,538				33,903,237
Administrative expenses			740,219				721,036
Total deductions			33,121,757				34,624,273
Net increase			56,524,511				60,873,982
Net assets available for benefits
Beginning of year			349,042,835				288,168,853
End of year		$	405,567,346			$	349,042,835

The accompanying notes are an integral part of these financial statements.

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

1.		Major Features of the Plan
		Background
		WESCO Distribution, Inc. Retirement Savings Plan (the “Plan”) was established as of February 28, 1994 (date of inception). At the date of inception, certain employees of the predecessor company became employees of WESCO Distribution, Inc. (the “Company”) and participants in the Plan. At the date of inception, all funds held by the prior plans of the predecessor company related to the employees of the Company were transferred to the Plan.
		The Plan is a participant-directed defined contribution plan covering certain employees of the Company and former employees with a fund balance of at least $5,000 who elected to maintain their funds in the Plan. Former employees cannot make contributions to the Plan.
		Participation for eligible employees requires an employee to be scheduled to work at least 1,000 hours per year and requires an employee to be paid through the Plan sponsor’s payroll system.
		Contributions
		The Plan is subject to the Employee Retirement Income Security Act of 1974, as amended (“ERISA”). Participants may elect to make tax deferred contributions ranging from 1% up to the lesser of 50% of their eligible compensation or $16,500. The $16,500 limit may be adjusted in future years by the Internal Revenue Service (“IRS”). The sum of the tax deferred contributions and the after-tax contributions cannot exceed 50% of the participant’s eligible compensation. Subject to limitation, the Company will make matching contributions in an amount equal to 50% of a participant’s total monthly contributions up to a maximum of 3% of their compensation. Also, the Company may, at the Board of Directors’ discretion, make a discretionary contribution to the Plan provided certain predetermined profit levels are attained.
		Effective August 1, 2009, the Company suspended employer matching and discretionary contributions; accordingly, no discretionary contributions were made for the Plan’s fiscal year ended December 29, 2009. Effective January 1, 2010, the Company reinstated employer matching and discretionary contributions that had been suspended since August 1, 2009. Discretionary contributions of $13,335,799 were made for the Plan’s fiscal year ended December 29, 2010.
		The Plan includes a negative enrollment policy. Under this policy, if an individual does not submit an automatic enrollment waiver or elect a deferral rate, the employee will be automatically enrolled in the Plan at a 3% deferral rate. The deferral rate is increased by 1% each September 1 until the deferral rate equals 6%.
		Participants who have attained age 50 before the close of the plan year are eligible to make catch-up contributions in addition to pre-tax contributions. A catch-up contribution is a pre-tax contribution that exceeds the annual deferral limit. A participant’s total catch-up contribution cannot exceed $5,500. The catch up contribution limits are determined by the IRS and then indexed for inflation. In addition to cash, in-kind contributions are permitted which may consist of stocks, bonds, property or other securities.

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

		Vesting
		Participants are fully vested in the value of their contributions and related investment income at all times and vest in their allocated share of employer matching and discretionary contributions according to the following table:

Less than two years of service			0	%
Two years of service			20	%
Three years of service			40	%
Four years of service			66	%
Five or more years of service			100	%

		In conjunction with a leveraged recapitalization of the Company, all active employees as of June 5, 1998 became fully vested.
		Forfeitures
		Employer contributions forfeited by participants not vested at their termination date are used to reinstate previously forfeited account balances of former participants who have returned to the Company, reduce employer contributions in accordance with the Plan’s provisions or pay Plan expenses. Total forfeitures that reduced employer contributions in both 2010 and 2009 were approximately $1,389,000 and $1,099,000, respectively. As of December 29, 2010, a balance of approximately $54,000 was available to reduce employer contributions in 2011.
		Participant Accounts
		An account is maintained for each participant, which is credited with the participant’s and the employer’s matching contributions and an allocation of employer’s discretionary contributions, plan earnings and administrative expenses. Allocations are based on participant contributions or account balances, as defined by the Plan. The benefit to which a participant is entitled is the benefit that can be provided from the participant’s vested account balance.
2.		Summary of Significant Accounting Policies
		Accounting Principles
		The financial statements of the Plan have been prepared in accordance with accounting principles generally accepted in the United States of America. The following are the significant accounting policies followed by the Plan:
		Basis of Accounting
		The accounting records of the Plan are maintained on the accrual basis of accounting.
		Recent Accounting Pronouncements
		In September 2010, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update 2010-25, Reporting Loans to Participants by Defined Contribution Pension Plans (ASU 2010-25). ASU 2010-25 requires participant loans to be measured at their unpaid principal balance plus any accrued but unpaid interest and to be classified as notes receivable from participants. Previously, loans were measured at fair value and classified as investments. Participant loans have been reclassified to promissory notes receivable from participants as of December 29, 2010 and December 29, 2009. Interest income related to promissory notes is included in interest and dividend income.

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

		In January 2010, the FASB issued Accounting Standards Update 2010-06, Improving Disclosures about Fair Value Measurements (ASU 2010-06). ASU 2010-06 amended Accounting Standards Codification 820, Fair Value Measurements and Disclosures (ASC 820), to clarify certain existing fair value disclosures and to require a number of additional disclosures. The guidance in ASU 2010-06 clarified that disclosures should be presented separately for each “class” of assets and liabilities measured at fair value and provided guidance on how to determine the appropriate classes of assets and liabilities to be presented. ASU 2010-06 also clarified the requirement for entities to disclose information about both the valuation techniques and inputs used in estimating Level 2 and Level 3 fair value measurements. In addition, ASU 2010-06 introduced new requirements to disclose the amounts (on a gross basis) and reasons for any significant transfers between Levels 1, 2, and 3 of the fair value hierarchy and to present information regarding the purchases, sales, issuances, and settlements of Level 3 assets and liabilities on a gross basis. With the exception of the requirement to present changes in Level 3 measurements on a gross basis, which is delayed until 2011, the guidance in ASU 2010-06 is effective for reporting periods beginning after December 15, 2009. The adoption did not impact the Plan’s net assets available for benefits or its changes in net assets available for benefits. Refer to Note 4, Investments, for required disclosures.
		Other pronouncements issued by the FASB or other authoritative accounting standard groups with future effective dates are either not applicable or not expected to be significant to the Plan.
		Investment Valuation and Income Recognition
		The Plan has adopted a framework for measuring fair value under current accounting pronouncements that requires fair value measurements and enhanced disclosures about fair value measurements. This framework defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction. Disclosures include a fair value hierarchy which requires an entity to maximize the use of observable inputs when measuring fair value.
		The three levels of inputs that may be used to measure fair value are as follows:

	•		Level 1 – Observable inputs such as quoted prices in active markets for identical investments that the Plan has the ability to access.
	•		Level 2 – Inputs include:

	1.		Quoted prices for similar assets or liabilities in active markets;
	2.		Quoted prices for identical or similar assets or liabilities in inactive markets;
	3.		Inputs, other than quoted prices in active markets, that are observable either directly or indirectly;
	4.		Inputs that are derived principally from, or corroborated by, observable market data by correlation or other means.

•

Level 3 – Unobservable inputs in which there is little or no market activity for the asset or liability, which require the reporting entity to develop its own estimates and assumptions relating to the pricing of the asset or liability, including assumptions regarding risk.

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

		The asset’s or liability’s fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.
		Following is a description of the valuation methodologies used for assets measured at fair value. There have been no changes in the methodologies used as of December 29, 2010 and 2009.

	•		Common stocks, corporate bonds and U.S. government securities are valued at the closing price reported on the active market on which the individual securities are traded.
	•		Registered investment companies are valued at the net asset value of shares held by the Plan as of December 29.
	•		Common collective trusts are valued at fair value by determining the price of the underlying investments. Equities listed on an exchange are valued at the latest quoted sales price of the exchange on which the security is primarily traded. Securities that are not traded on the valuation date or securities that are not listed on an exchange are valued at the latest bid price provided by the trust’s pricing service.
	•		The Stable Value Fund (Note 7) is valued based on the underlying securities which include corporate bonds, commercial mortgage-backed securities and government securities.
	•		The RAFI Enhanced Large Company Fund is valued based on the underlying securities which include common stocks.

		The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while the Plan believes its valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement as of the reporting date.
		Investment contracts held by a defined-contribution plan are required to be reported at fair value. However, contract value is the relevant measurement attribute for that portion of the net assets available for benefits of a defined-contribution plan attributable to fully benefit-responsive investment contracts, because contract value is the amount participants would receive if they were to initiate permitted transactions under the terms of the plan. As required by current accounting pronouncements, the statement of net assets available for benefits presents the fair value of the investment contracts as well as the adjustment of the fully benefit-responsive investment contracts from fair value to contract value. The statement of changes in net assets available for benefits is prepared on a contract value basis.
		Purchases and sales of securities are recorded on a trade date basis. Dividends are recorded on the ex-dividend date. Interest income is recorded on an accrual basis.
		Net Appreciation in Value of Investments
		The Plan presents in the statement of changes in net assets available for benefits the net appreciation in the fair value of its investments, consisting of realized gains (losses) and unrealized gains (losses) in the registered investment companies, common collective trusts, Stable Value Fund, RAFI Enhanced Large Company Fund, WESCO International stock and other common stocks.

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

		Use of Estimates
		The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make significant estimates and assumptions. These estimates may affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of additions and deductions during the reporting period. Actual results could differ from those estimates.
		Risks and Uncertainties
		The Plan provides for various investment options in any combination of stocks, bonds, fixed income securities and other investment securities. Investment securities are exposed to various risks, such as interest rate, market and credit risk. Due to the level of risk associated with certain investment securities and the level of uncertainty related to changes in the value of investment securities, it is at least reasonably possible that changes in the near-term could materially affect (i) participants’ account balances, and (ii) the amounts reported in the (a) statements of net assets available for benefits and the (b) statements of changes in net assets available for benefits.
		Other
		All administrative expenses were paid by the Plan during 2010 and 2009.
		Payment of Benefits
		Benefits are recorded when paid.
3.		Tax Status
		The IRS has determined and informed the Company by a letter dated October 15, 2003, that the Plan is designed in accordance with Section 401(a) of the Internal Revenue Code (“IRC”) and, therefore, is exempt from federal taxes under provisions of Section 501(a). Accordingly, no provision for income taxes has been included in the Plan’s financial statements. The Plan has been amended since receiving its determination letter. However, the Plan administrator and the Plan’s tax counsel believe the Plan is designed and is currently being operated in compliance with the applicable requirements of the IRC.

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

4.		Investments
		The following tables sets forth the fair value of the Plan’s assets by level, as described in Note 2, as of December 29, 2010 and 2009:

		December 29, 2010
		Level 1				Level 2				Level 3				Total
Shares of registered investment companies:
Small growth		$	2,324,761			$	—			$	—			$	2,324,761
Small value			1,788,814				—				—				1,788,814
Large growth			35,447,600				—				—				35,447,600
Large value			13,466,588				—				—				13,466,588
Moderate allocation			43,962,362				—				—				43,962,362
Mid-cap value			21,629,071				—				—				21,629,071
Mid-cap growth			42,693,921				—				—				42,693,921
Foreign large blend			24,894,918				—				—				24,894,918
Intermediate-term bond			20,122,299				—				—				20,122,299
Total shares of registered investment companies			206,330,334				—				—				206,330,334
Common collective trusts:
Conservative allocation			—				4,254,078				—				4,254,078
Moderate allocation			—				9,513,259				—				9,513,259
Large blend			—				8,327,639				—				8,327,639
Total common collective trusts			—				22,094,976				—				22,094,976
Stock funds and self-directed accounts:
WESCO International Pooled Stock Fund			16,466,959				—				—				16,466,959
Self-directed accounts:
Cash and cash equivalents			898				—				—				898

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

		December 29, 2010 (continued)
		Level 1				Level 2				Level 3				Total
Self-directed accounts (continued):
Preferred stock			7				—				—				7
Common stock:
Transportation			191,351				—				—				191,351
Food, Beverages & Tobacco			127,927				—				—				127,927
Building Materials			59,007				—				—				59,007
Chemicals			23,031				—				—				23,031
Communications & Media			136,320				—				—				136,320
Electronics & Equipment			797,617				—				—				797,617
Energy			134,341				—				—				134,341
Financial			480,782				—				—				480,782
Health Care Services			219,290				—				—				219,290
Industrial			80,421				—				—				80,421
Leisure & Entertainment			197,648				—				—				197,648
Metals			163,041				—				—				163,041
Miscellaneous			264,363				—				—				264,363
Multi-Industry			149,379				—				—				149,379
Retail			42,607				—				—				42,607
Utilities			233,921				—				—				233,921
Mutual funds:
Short term			958,205				—				—				958,205
Fixed			307,421				—				—				307,421
Balanced			314,066				—				—				314,066
Equity			1,509,772				—				—				1,509,772
International			405,040				—				—				405,040
Total stock funds and self-directed accounts			23,263,414				—				—				23,263,414
Stable Value Fund			—				112,092,798				—				112,092,798
RAFI Enhanced Large Company Fund:
Cash and cash equivalents			—				291,309				—				291,309
Common stock:
Consumer discretionary			—				2,978,260				—				2,978,260
Consumer staples			—				2,138,452				—				2,138,452
Energy			—				2,833,331				—				2,833,331
Financials			—				4,617,255				—				4,617,255

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

		December 29, 2010 (continued)
		Level 1				Level 2				Level 3				Total
RAFI Enhanced Large Company Fund (continued):
Common stock (continued):
Health care			—				1,933,118				—				1,933,118
Industrials			—				2,879,403				—				2,879,403
Information technology			—				2,429,792				—				2,429,792
Materials			—				839,713				—				839,713
Telecommunication services			—				854,860				—				854,860
Utilities			—				1,357,052				—				1,357,052
Total RAFI Enhanced Large Company Fund			—				23,152,545				—				23,152,545
		$	229,593,748			$	157,340,319			$	—			$	386,934,067

		December 29, 2009
		Level 1				Level 2				Level 3				Total
Shares of registered investment companies:
Large growth		$	32,383,031			$	—			$	—			$	32,383,031
Large value			12,710,956				—				—				12,710,956
Moderate allocation			38,040,908				—				—				38,040,908
Mid-cap value			18,139,384				—				—				18,139,384
Mid-cap growth			36,535,462				—				—				36,535,462
Foreign large blend			22,944,653				—				—				22,944,653
Intermediate-term Bond			16,813,799				—				—				16,813,799
Total shares of registered investment companies			177,568,193				—				—				177,568,193
Common collective trusts:
Conservative allocation			—				3,981,272				—				3,981,272
Moderate allocation			—				8,719,955				—				8,719,955
Large blend			—				7,373,154				—				7,373,154
Total common collective trusts			—				20,074,381				—				20,074,381

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

		December 29, 2009 (continued)
		Level 1				Level 2				Level 3				Total
Stock funds and self-directed accounts:
WESCO International Pooled Stock Fund			8,475,131				—				—				8,475,131
Self-directed accounts:
Preferred stock			52				—				—				52
Common stock:
Transportation			107,212				—				—				107,212
Food, Beverages & Tobacco			92,756				—				—				92,756
Building Materials			54,666				—				—				54,666
Chemicals			26,509				—				—				26,509
Communications & Media			115,411				—				—				115,411
Electronics & Equipment			423,945				—				—				423,945
Energy			232,054				—				—				232,054
Financial			188,250				—				—				188,250
Health Care Services			116,538				—				—				116,538
Industrial			273,966				—				—				273,966
Leisure & Entertainment			194,241				—				—				194,241
Metals			73,107				—				—				73,107
Miscellaneous			173,694				—				—				173,694
Multi-Industry			220,872				—				—				220,872
Retail			36,676				—				—				36,676
Utilities			232,965				—				—				232,965
Rights and warrants			136				—				—				136
Mutual funds:
Short term			1,069,271				—				—				1,069,271
Fixed			926,120				—				—				926,120
Balanced			314,367				—				—				314,367
Equity			2,079,554				—				—				2,079,554
International			296,691				—				—				296,691
Total stock funds and self-directed accounts			15,724,184				—				—				15,724,184
Stable Value Fund			—				109,219,294				—				109,219,294

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

		December 29, 2009 (continued)
		Level 1				Level 2				Level 3				Total
RAFI Enhanced Large Company Fund:
Cash and cash equivalents			—				380,241				—				380,241
Common stock:
Consumer discretionary			—				2,626,885				—				2,626,885
Consumer staples			—				1,880,205				—				1,880,205
Energy			—				2,222,556				—				2,222,556
Financials			—				4,726,850				—				4,726,850
Health care			—				1,898,507				—				1,898,507
Industrials			—				2,270,682				—				2,270,682
Information technology			—				2,294,983				—				2,294,983
Materials			—				935,099				—				935,099
Telecommunication services			—				646,767				—				646,767
Utilities			—				1,063,805				—				1,063,805
Total RAFI Enhanced Large Company Fund			—				20,946,580				—				20,946,580
		$	193,292,377			$	150,240,255			$	—			$	343,532,632

Investments (at fair value) representing 5% or more of the net assets available for benefits as of December 29, 2010 and 2009 were as follows:

		2010				2009
AMCAP Fund (Class R-5)		$	35,447,600			$	—
AMCAP Fund (Class R-4)			—				32,383,031
American Balanced Fund (Class A)			43,962,362				38,040,908
Columbia Acorn Fund (Class A)			42,693,921				26,925,313
Columbia Mid Cap Value Fund (Class A)*			21,629,071				—
RiverSource Midcap Value Fund *			—				18,139,384
Stable Value Fund			112,092,798				109,219,294
Thornburg International Value Fund			24,894,918				22,944,653

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

5.		Promissory Notes From Participants
		Participants are permitted to borrow against a portion of their vested account balance, pursuant to nondiscriminatory rules established by the Administrative Committee, up to a maximum of $50,000 or 50% of their vested account balance. Each promissory note is to be repaid over a period not to exceed five years.
		The interest rate applied to promissory notes is established each month by the Administrative Committee at 1% above the PNC Bank prime interest rate. The interest rate on notes outstanding ranged between 4.25% and 10.5% for the fiscal years ended December 29, 2010 and 2009. Principal and interest payments are generally made through monthly payroll deductions and are credited to the participant’s individual account. Promissory notes of approximately $6,542,000 and $5,965,000 were made from the Plan and note principal repayments of approximately $4,552,000 and $4,028,000 were received by the Plan for the fiscal years ended December 29, 2010 and 2009, respectively. Interest on the promissory notes of approximately $522,000 and $501,000 was earned by the Plan for the fiscal years ended December 29, 2010 and 2009, respectively.
6.		Plan Termination
		Although the Company has not expressed any intent to do so, it has the right under the Plan to discontinue its contributions at any time and to terminate the Plan subject to the provisions of ERISA. In the event the Plan terminates, participants will become 100% vested in their accounts, and all vested assets shall be distributed to the participants in accordance with the terms of the Plan, or in such other manner, not inconsistent with the requirements of any applicable law or regulation, as the Company may in its sole discretion determine.
7.		The Stable Value Fund
		During 2007, the Plan began investing in a fully benefit-responsive synthetic guaranteed interest contract (“GIC”) with an insurance company as part of offering the Stable Value Fund (the “Fund”) investment option to participants. Contributions to this Fund are used to purchase units of a collective trust vehicle which is invested in high-quality U.S. bonds, including U.S. government treasuries, corporate debt securities, and other high-credit-quality asset-backed securities. The GIC issuer is contractually obligated to repay the principal and a specified interest rate that is guaranteed to the Plan. There are no reserves against contract value for credit risk of the contract issuer or otherwise.
		The Fund has entered into a wrap contract with an insurance company under which the insurance company provides a guarantee with respect to the availability of funds to make distributions from this investment option. This insurance contract is carried at contract value in the participants’ accounts.
		Participant accounts in the Fund are credited with interest at a fixed rate that is reset quarterly based on an agreed-upon formula as defined in the contract. The primary variables which could impact the future interest rates that are credited to the participant’s accounts (“credited rates”) include (i) the amount and timing of participant contributions, (ii) transfers and withdrawals into/out of the contract, (iii) the current yield of the assets underlying the contract, (iv) the duration of the assets underlying the contract, and (v) the existing

WESCO Distribution, Inc.
Retirement Savings Plan
Notes to Financial Statements
December 29, 2010 and 2009

		difference between fair value of the securities and the contract value of the assets within the insurance contract. The credited rate of security-backed contracts will track current market yields on a trailing basis. The rate reset feature allows the contract value to converge with the fair value of the underlying portfolio over time, assuming the portfolio continues to earn the current yield for a period of time equal to the current portfolio duration.
		To the extent that the underlying portfolio has unrealized and/or realized losses, a positive adjustment is made when reconciling from fair value to contract value under contract value accounting. As a result, the future credited rate may be lower over time than the current market rates. Similarly, if the underlying portfolio generates unrealized and/or realized gains, a negative adjustment is made when reconciling from fair value to contract value, and in the future, the credited rate may be higher than the current market rates. The insurance contract cannot credit an interest rate that is less than zero percent.
		Certain events limit the ability of the Plan to transact at contract value with the insurance company. Such events are limited to premature termination of the contract by the Plan or plan termination. The plan sponsor has not expressed any intention to take either of these actions.
		As described in Note 2, because the synthetic GIC is fully benefit-responsive, contract value is the relevant measurement attribute for that portion of the net assets available for benefits attributable to the synthetic GICs. Participants may ordinarily direct the withdrawal or transfer of all or a portion of their investment at contract value. The average yields earned by the Fund as of December 29, 2010 and 2009 are as follows:

Average yield for synthetic GICs		2010				2009
Based on actual earnings			2.76	%			3.44	%
Based on interest rate credited to participants			4.43	%			4.67	%

8.		Related Party Transactions
		Participants of the Plan may elect to invest in WESCO International, Inc. common stock within the WESCO Pooled Stock Fund. WESCO International, Inc. owns 100% of the Company. Therefore, these transactions qualify as party-in-interest transactions. Purchases and sales proceeds within the WESCO Pooled Stock Fund for 2010 were $2,605,000 and $2,210,000, respectively, and purchases and sales proceeds for 2009 were $2,754,000 and $3,086,000, respectively.
9.		Subsequent Event
		As a result of the acquisition of the business of TVC Communications, LLC on December 16, 2010, approximately 250 participants were added to the Plan. These participants transferred assets of approximately $12,550,000 to the Plan in 2011.

WESCO Distribution, Inc.
Retirement Savings Plan
Schedule of Assets (Held at End of Year)
EIN 25-1723345, Plan Number 001
December 29, 2010		Schedule H, line 4i

(a)		(b)		(c)		(d)
				Description of Investment
		Identity of Issue,		Including Maturity Date,
		Borrower, Lessor or		Rate of Interest, Collateral,		Current
		Similar Party		Par, or Maturity Value		Value
		AMCAP Fund		AMCAP Fund (Class R-5)		$	35,447,600
		American Funds		American Balanced Fund (Class A)			43,962,362
		Baron Funds		Baron Small Cap Fund			2,324,761
		Columbia Mutual Funds		Columbia Acorn Fund (Class A)			42,693,921
		Columbia Mutual Funds		Columbia Mid Cap Value Fund (Class A)			21,629,071
		Diamond Hill Family of Funds		Diamond Hill Small Cap Fund			1,788,814
		Loomis Sayles		Loomis Sayles Invest Grade Bond			20,122,299
		MFS Family of Funds		MFS Value Fund (Class A)			13,466,588
		Thornburg International		Thornburg International Value Fund			24,894,918
		Registered Investment Companies Total					206,330,334
		Manning & Napier Promix Funds		Manning & Napier Promix Conservative Trust			4,254,078
		Manning & Napier Promix Funds		Manning & Napier Promix Extended Trust			5,616,874
		Manning & Napier Promix Funds		Manning &Napier Promix Maximum Trust			8,327,639
		Manning & Napier Promix Funds		Manning & Napier Promix Moderate Trust			3,896,385
		Common Collective Trusts Total					22,094,976
*		WESCO International, Inc.		WESCO International Pooled Stock Fund			16,466,959
		3M Company		Common Stock			15,270
		Ameriprise Cash		Cash and cash equivalents			899
		Abbott Labs		Common Stock			4,742
		ADR Cemex		Common Stock			11,632
		Adolph Coors		Common Stock			5,034
		Advanced Energy Industries		Common Stock			3,128
		AEP Industries Inc.		Common Stock			5,192
		AGL Resources		Common Stock			36,190
		Agnico Eagle Mines LTD		Common Stock			17,666
		Aimco		Common Stock			9,065
		Alcatel-Lucent Ads		Common Stock			3,079
		Alcoa Inc.		Common Stock			15,657
		Allergan Inc.		Common Stock			13,862
		Allete Inc.		Common Stock			16,902
		Allos Therapeutics Inc.		Common Stock			2,325
		Ambac Financial Group		Common Stock			360
		American Beacon Funds		Large Cap Value Fund			7,164
		American Capital Agency Corp		Common Stock			9,450
		American Century Funds		High Yield Fund			30,125
		Amtech Systems Inc		Common Stock			23,643
		Annaly Capital Management Inc.		Common Stock			167,873
		Anworth Mortgage Asset Corp		Common Stock			81,932
		AOL Inc.		Common Stock			1,518
		Apple Inc.		Common Stock			198,102

WESCO Distribution, Inc.
Retirement Savings Plan
Schedule of Assets (Held at End of Year)
EIN 25-1723345, Plan Number 001
December 29, 2010		Schedule H, line 4i

(a)		(b)		(c)		(d)
				Description of Investment
		Identity of Issue,		Including Maturity Date,
		Borrower, Lessor or		Rate of Interest, Collateral,		Current
		Similar Party		Par, or Maturity Value		Value
		Applied Materials		Common Stock			1,370
		Arcadia Resources, Inc.		Common Stock			153
		Artisan Funds		International Investor Shrs			5,758
		AT&T Inc		Common Stock			28,724
		Atlas Pipeline Partners LP		Common Stock			6
		Authentec Inc.		Common Stock			7,285
		Azteca Gold Corp		Common Stock			1,215
		B & G Foods Inc.		Common Stock			51,892
		Baidu.com Inc.		Common Stock			205,653
		Bank America Corp		Common Stock			1,331
		Barclays Bank Plc		Common Stock			2,688
		Barclays Bank Plc		iPath Index Lkd Secs Lkd to Dow			4,858
		Berkshire Hathaway Inc.		Common Stock			11,983
		Bhp Billiton Ltp-Spon Adr		Common Stock			16,240
		Biotime Inc.		Common Stock			240
		Boeing Co.		Common Stock			26,020
		BP Plc		Common Stock			8,091
		Buffalo		Small Cap Fund			13,952
		By Prudhoe Bay Royalty Trust		Common Stock			5,103
		Camelot Information Systems Inc.		Common Stock			67,146
		CanWest Petroleum Inc.		Common Stock			1,287
		Cardium Therapeutics Inc.		Common Stock			3,681
		Caterpillar Inc.		Common Stock			28,389
		CBS Corp. Class B		Common Stock			73,860
		Cef Select Sector SPDR		Common Stock			43,146
		Celgene Corp.		Common Stock			17,919
		Cell Therapeutics		Common Stock			1,122
		Cheniere Energy Inc		Common Stock			1,136
		Chevron Corp.		Common Stock			9,137
		Cinemark Holdings Inc.		Common Stock			3,446
		Circuit City Stores		Common Stock			3
		Citigroup Inc.		Common Stock			84,667
		Citizens Communications Corporation		Common Stock			232
		China Telecom Group Inc.		Common Stock			459
		Clinical Data Inc.		Common Stock			4,286
		Columbia		Mid Cap Growth Opportunity Fund			33,973
		Columbia		Global Bond Fund — Class R4			119,836
		Columbia		Seligman Global Technology Fund			43,491
		Compass Minerals International		Common Stock			17,932
		Core-Mark Holding Co Inc.		Common Stock			7,320
		Coronado Res LTD		Common Stock			3,754
		Corporate Exec Board		Common Stock			3,859
		Costco Whsl Corp.		Common Stock			7,779

WESCO Distribution, Inc.
Retirement Savings Plan
Schedule of Assets (Held at End of Year)
EIN 25-1723345, Plan Number 001
December 29, 2010		Schedule H, line 4i

(a)		(b)		(c)		(d)
				Description of Investment
		Identity of Issue,		Including Maturity Date,
		Borrower, Lessor or		Rate of Interest, Collateral,		Current
		Similar Party		Par, or Maturity Value		Value
		CrossTex Energy Inc		Common Stock			2,724
		CSR PLC Cambridge		Common Stock			798
		CTS Corp.		Common Stock			1,111
		Cubist Pharmaceuticals		Common Stock			4,328
		CVS Caremark Corporation		Common Stock			6,980
		Deere & Co		Common Stock			8,486
		Del Global Technologies Corp.		Common Stock			80
		Deliste Incorporated		Common Stock			1
		Dex One Corp		Common Stock			813
		Direxion		ETF Trust Daily Financial Bear 3X			32,970
		Discovery Laboratories Inc.		Common Stock			1,080
		Dodge & Cox Funds		Balanced Fund			132,081
		Dodge & Cox Funds		Income Fund			80,847
		Dodge & Cox Funds		Stock Fund			40,304
		Dorchester Minerals LP		Common Stock			2,733
		Dow Chemical		Common Stock			14,364
		Duluth Metals LTD		Common Stock			8,880
		Dynamic Materials Corp.		Common Stock			2,057
		EI Dupont De Nemours		Common Stock			5,002
		El Dorado Gold Corp		Common Stock			5,553
		E Trade Financial Corp.		Common Stock			7,985
		Eaton Corp.		Common Stock			76,050
		Enerplus Resources		Trust Unit Series G Fund			9,841
		EON AG.SP ADR		Common Stock			6,045
		Excellon Resources Inc.		Common Stock			1,096
		Excelsior Funds		Value & Restructuring Fund			13,612
		Exide Technologies		Common Stock			47,000
		Exxon Mobil Corp.		Common Stock			20,103
		Fibertower Corp.		Common Stock			5,376
		First Horizon National Corp		Common Stock			3,817
		First Niagara Financial Group		Common Stock			4,507
		Ford Motor Company		Common Stock			30,550
		Forest Labs		Common Stock			9,615
		Fortescue Metal Group LTD		Common Stock			1,020
		Franconia Minerals Corp.		Common Stock			4,816
		Freeport McMoran Copper & Gold Inc.		Common Stock			54,809
		Fuel-Tech		Common Stock			4,820
		Furiex Pharmaceuticals Inc.		Common Stock			2,844
		Gabelli		Asset Fund			44,618
		Gabelli		Utilities Fund			37,483
		Gamco International Growth AAA		Foreign Large Growth Fund			19,110
		General Electric		Common Stock			130,159
		General Money Market Fund Inc. Class A		General Money Market Fund			958,205

WESCO Distribution, Inc.
Retirement Savings Plan
Schedule of Assets (Held at End of Year)
EIN 25-1723345, Plan Number 001
December 29, 2010		Schedule H, line 4i

(a)		(b)		(c)		(d)
				Description of Investment
		Identity of Issue,		Including Maturity Date,
		Borrower, Lessor or		Rate of Interest, Collateral,		Current
		Similar Party		Par, or Maturity Value		Value
		Genon Energy Inc.		Common Stock			5,895
		Genzyme Corp.		Common Stock			7,113
		Globe Specialty Mines Inc.		Common Stock			6,892
		Goldcorp Inc.		Common Stock			4,558
		Harbor Funds		Bond Fund — Institutional Class			12,471
		Hatteras Financial Corp		Common Stock			17,239
		Hawaiian Electric Ind. Inc.		Common Stock			24,730
		Headwaters Inc.		Common Stock			1,932
		Heartland Funds		Select Value Fund			26,303
		Hewlett Packard		Common Stock			8,464
		I Shares		Silver Trust			13,442
		I Shares		MSCI Australia Index Fund			15,258
		I Shares		MSCI Canada Index Fund			23,832
		I Shares		TR IBOXX High Yield Corporate Bond Fund			2,701
		I Shares		S&P Global Telecom Fund			11,605
		I Shares		DJ Select Dividend Index Fund			9,014
		I Shares		S&P Global 100			4,980
		I Shares		S&P Gloal Finl Sector			5,064
		I Shares		DJ U.S. Consumer Cycl SEC Fund			3,393
		I Shares		TR Dow Jones US Aerospace & Defense Equity Fund			8,839
		Icon Funds		Icon Healthcare Fund			44,785
		IGO Inc.		Common Stock			46,919
		Illumina Inc.		Common Stock			105,666
		Impala Platinum Spon ADR		Common Stock			3,475
		Inergy LP		Common Stock			12,566
		Integral Technologies Inc.		Common Stock			4,104
		Intel Corp.		Common Stock			2,094
		Interplay Entertainment		Common Stock			70
		Intl Speedway		Common Stock			7,468
		Invio Biomedical Corp.		Common Stock			1,740
		Ivanhoe Energy, Inc.		Common Stock			280
		Janus Funds		Global Technology Fund			16,162
		Janus Funds		Overseas Fund			57,905
		Janus Funds		Mid Cap Value Fund			18,589
		Janus Funds		Enterprise Fund			24,842
		Janus Funds		Special Equity Fund			14,198
		Janus Funds		Orion Fund			12,314
		Johnson & Johnson		Common Stock			5,157
		Joy Global Inc.		Common Stock			17,404
		Keryx Biopharmaceuticals		Common Stock			938
		Kinder Morgan Energy Partners LP		Common Stock			17,525
		Klondike Silver Corp.		Common Stock			3
		Koko Petroleum Inc.		Common Stock			1

WESCO Distribution, Inc. Retirement Savings Plan Schedule of Assets (Held at End of Year) EIN 25-1723345, Plan Number 001 December 29, 2010		Schedule H, line 4i

(a)		(b)		(c)		(d)
				Description of Investment
		Identity of Issue,		Including Maturity Date,
		Borrower, Lessor or		Rate of Interest, Collateral,		Current
		Similar Party		Par, or Maturity Value		Value
		Lehman Brothers Holdings Inc		Preferred Stock			7
		Loomis Sayles		Global Bond Fund			135,814
		Lowes Companies		Common Stock			7,509
		Managers		Real Estate Securities Fund			20,345
		Managers Intermediate Duration Govt		Fixed Fund			51,088
		Manhattan Pharmaceuticals		Common Stock			96
		Mannkind Corp		Common Stock			1,802
		Marathon Oil Corp		Common Stock			58
		Marina Biotech Inc.		Common Stock			80
		Marisco		21st Century Mutual Fund			7,868
		Marsico		Large Growth Fund			27,539
		Market Vectors ETF TR		Agribusiness Fund			7,891
		Marvell Technology Group		Common Stock			3,688
		Masco Corp		Common Stock			38,130
		Matrix Advisors		Value Fund			43,884
		Maxwell Technologies Inc		Common Stock			756
		Medoro Res LTD		Common Stock			190
		Merck & Co.		Common Stock			8,509
		Metalico Inc.		Common Stock			1,948
		Microsoft Corp.		Common Stock			2,887
		Monsanto Company		Common Stock			13,913
		Mosaic Co.		Common Stock			3,665
		Myiad Genetics		Common Stock			6,126
		Myriad Pharmaceuticals Inc.		Common Stock			1,266
		Nacel Energy Corp.		Common Stock			297
		Neomedia Technologies		Common Stock			15
		Nestle SA Sponsored ADR		Common Stock			14,795
		Netapp, Inc.		Common Stock			87,536
		Neuberger Berman		Real Estate Fund			18,979
		Newcastle Investment Corp.		Common Stock			1,297
		Nokia Corp.		Common Stock			3,335
		Nvdia Corp		Common Stock			2,241
		NWM Mining Corp		Common Stock			1,417
		Oakmark Funds		Global Fund			58,077
		Oakmark Funds		Mutual Fund			14,785
		Oakmark Funds		Oakmark Equity and Income Fund (I)			41,285
		Oakmark Funds		International Fund (Class I)			65,760
		Oshkosh Corporation		Common Stock			11,453
		Palomar Medical Tech		Common Stock			29,620
		Paychex Inc.		Common Stock			4,635
		Pengrowth Energy Trust		Common Stock			15,480
		Petroquest Energy Inc.		Common Stock			3,685
		Petroleo Brasileiro SA Petrobas Sponsored ADR		Common Stock			367

WESCO Distribution, Inc. Retirement Savings Plan Schedule of Assets (Held at End of Year) EIN 25-1723345, Plan Number 001 December 29, 2010		Schedule H, line 4i

(a)		(b)		(c)		(d)
				Description of Investment
		Identity of Issue,		Including Maturity Date,
		Borrower, Lessor or		Rate of Interest, Collateral,		Current
		Similar Party		Par, or Maturity Value		Value
		Pfizer Inc.		Common Stock			3,887
		Philip Morris International Inc.		Common Stock			11,750
		PIMCO Funds		Real Return Fund			10,352
		PNM Resources Inc.		Common Stock			59,445
		Polymet Mining Corp.		Common Stock			18,115
		Potash Corp of Saskatchewan		Common Stock			30,543
		Powershares		Agricultural Fund			7,104
		Powershares		Global Water Portfolio Fund			11,484
		Prestige Brand Holdings		Common Stock			9,560
		Proshares TR		Ultrashort Lehman 20 Year Fund			167,271
		Qualcomm Inc.		Common Stock			2,500
		Rayonier Inc		Common Stock			1,067
		RF Micro-Devices		Common Stock			22,290
		Rio Tinto PLC ADR		Common Stock			21,246
		Riverbed Technology Inc.		Common Stock			88,450
		Royal Dutch Shell PLC Sponsored ADR		Common Stock			10,632
		Royce		Total Return Fund			7,625
		RS Partners		Growth Fund			4,902
		Safeway Inc.		Common Stock			5,583
		Seadrill Limited		Common Stock			21,749
		Sequenom Inc.		Common Stock			324
		Short QQQ		Equity Fund			11,034
		Silver Grail Res LTD		Common Stock			3,540
		Silver Star Energy		Common Stock			5
		Sound Shore Fund		Common Stock			6,458
		Southern Copper Corp.		Common Stock			24,380
		SPDR		Series Trust Fund			5,743
		SSGA		International Stock Selection Fund			25,186
		St Joe Company		Common Stock			16,792
		Statiol ASA Group		Common Stock			38,806
		Strategic Resource Acquisition Corp		Common Stock			91
		Supergen Inc.		Common Stock			1,340
		Sysco Corp.		Common Stock			6,857
		T. Rowe Price Funds		Balanced Fund			106,745
		T. Rowe Price Funds		Capital Appreciation Fund			135,750
		T. Rowe Price Funds		Emerging Markets Bond Fund			114,172
		T. Rowe Price Funds		New Era Fund			130,714
		T. Rowe Price Funds		Growth Stock Fund			53,312
		T. Rowe Price Funds		Spectrum International Fund			18,042
		T. Rowe Price Funds		Dividend Growth Fund			5,221
		TCW Funds, Inc.		Focused Equities Fund			15,617
		Third Avenue		Real Estate Value Fund			5,652
		Third Avenue		International Value Fund			12,626

WESCO Distribution, Inc. Retirement Savings Plan Schedule of Assets (Held at End of Year) EIN 25-1723345, Plan Number 001 December 29, 2010		Schedule H, line 4i