March 18, 2009

WESCO International, Inc. B. Riley 10th Annual Las Vegas Investor Conference

Presenting:

John J. EngelSenior Vice President, Chief Operating Officer

Daniel A. BrailerVice President, Treasurer

Note: All statements made herein that are not historical facts should be considered as “forward-

looking statements” within the meaning of the Private Securities Litigation Act of 1995. Such

statements involve known and unknown risks, uncertainties and other factors that may cause

actual results to differ materially. Such risks, uncertainties and other factors include, but are not

limited to, debt level, changes in general economic conditions, fluctuations in interest rates,

increases in raw materials and labor costs, levels of competition and other factors described in

detail in Form 10-K for WESCO International, Inc. for the year ended December 31, 2007 and

any subsequent filings with the Securities & Exchange Commission. Any numerical or other

representations in this presentation do not represent guidance by management and should not

be construed as such.

Safe Harbor Statement

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WESCO Profile

…with industry-leading positions

Fortune 500 Company headquartered in Pittsburgh, PAOver 7,000 employees including 2,700 outside and inside sales personnelConsistent growth strategy of:

– Local market penetration with coordinated national programs

– Accretive acquisitions– Operational excellence and enterprise-

wide LEAN initiatives

Leading Market Positions:– National Account programs– Integrated Supply Services– OEM Direct materials– Electric Utility Distribution Grid

Low cost operatorInternational operations and global sourcing capabilitiesNorth American Branch Network

Market LeaderExtra-Effort Company

1922192219941994

19981998 19991999 20042004 20072006

Founded as the distribution arm of

Westinghouse Electric Corporation

Leveraged buyout by management and

Clayton, Dubilier & Rice

Leveraged recapitalization by the Cypress Group

Listed on the New York Stock Exchange

LEAN

Integrated Supply

Capital Structure Improvements

Organic Sales Growthand Acquisitions

National Accounts Program

Acquisition Program

Record Financial

Performance

2008

Sales force expansion

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WESCO- A strategic supply chain solutions provider

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Providing Broad Solutions To Large & Sophisticated

CustomersMultiple products and services

Broad geographic coverage

Deep penetration into customer processes

Difficult to disintermediate

WESCO - Serving large, fragmented markets

Electrical is $95 Billion Subset

MRO Market $400 BillionSignificant  Opportunities in Large Markets

Fragmented Supply Chain

Attractive Historical Growth

Thousands of electrical and industrial products manufacturers

Over 10,000 electrical and industrial distributors

Top five distributors – 26% share of electrical distribution industry

75% + of electrical products get to market through distribution

Continuing industry consolidation

$600 Billion Total

Addressable

Construction, MRO and

OEM Markets

5 5-6 % Growth (GDP + 2-3%) for over 20 years

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Major End MarketsEnd Market 2008 End Market Composition Key Market Drivers / Indicators Competitive Differentiators

Industrial 39%

National AccountsOEMIntegrated SupplyGeneral Industry

Capacity UtilizationIndustrial ProductionManufacturing EmploymentISM Purchasing Managers’ Index

Blue Chip Customers

National Accounts

Integrated Supply

OEM Direct Material Network

Product Breadth

Utility Programs

Global Capabilities

400 Branch Footprint

Low Cost Model

Integrated IT Platform

LEAN Initiatives

Construction 39%

Non-ResidentialData CommunicationsPre-Fabricated StructuresResidential

Construction starts/square footageRenovationsArchitecture Billings IndexMcGraw Hill / Reed / US Census

Utility 16%

Investor Owned UtilitiesPublic PowerUtility Contractors

New starts / installed metersT&D line extensionT&D grid maintenanceGeneration MRO, upgrades, expansions

CIG 6%

Government EducationHealthcare

Projects and macro spendGovernment spending in technology and renovation

Industrial Construction Utility

WESCO’s Product Mix and Leading Suppliers

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Leading Suppliers

ABB Belden

Burndy Comm Scope

Cooper Eaton

General Cable Hubbell

Legrand Lithonia

Okonite Panduit

Phillips Rockwell

Southwire Thomas & Betts

Double-Digit Growth Over Past 5 Years

– Fortune 100 Focus– Outsourced MRO Procurement

Functions– Integrating Supply Chain

Processes

10% CAGR Over Past 7 Years

– Fortune 1000 Companies with Multiple Sites

– Coordinated MRO and Project Procurement Activities

– Single Contract; Standardized Purchasing and Pricing

Local Market Growth Rate

– More than 400 Full Service Branches

– Multiple Market Segments– Over 110,000 Customers

Integrated SupplyNational Accounts Program

Extensive Local Market Penetration

…high barriers to entry

WESCO’s Organic Growth Business Model

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Acquisitions Since June 2005

Driving Growth Faster Than The Market- Acquisitions supplement organic growth, profitability & diversification

Annual Sales When Acquired

End Market Rationale

Communication Supply $630 DataCom National leadership platform

Carlton Bates $300 Industrial OEM Diversify industrial base into electronic and value added assemblies

Fastec / J-Mark $95 Manufactured Structures Consolidate leadership position; Asian sourcing

Monti Electric $20 Commercial Construction

Participate in rebuild of gulf coast region

Cascade $11 Industrial OEM Strengthen industrial automation and control

AA-Electric $20 Industrial OEM Geographic expansion

End Market Momentum

End Market Q4 2008 Sales Growth Comments

WESCO Consolidated - 2%• Sequential gross margin expansion• Cost reduction actions taken/being taken• Strong free cash flow and capital structure

Industrial - 3%• National Accounts and Integrated Supply sales up 2%• National Accounts opportunity pipeline at record level• High renewal rate continues

Construction/CIG - 5%• Backlog flat from 2007 year-end• Seeing increased delays with some cancellations• Economists forecast 10-15% decline

Data Communications - 2%

• Growth in government and enterprise customers• Low voltage, A/V and industrial wire markets down• Seven new markets entered; co-located in existing

branches

Utility + 7% • Sales to investor owned utilities up double digits• Public power market flat, contractor market down

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$0.6

$0.8

$1.0

$1.2

$1.4

$1.6

$1.8

2004

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 Q4

WESCO’s Focus on Value Drivers…yields superior results

Quarterly Sales Growth($ Billions)

$6.1 BillionSales

Earnings Per Share

Increasing Free Cash Flow($ Millions)

(1) Cash from operating activities – CAPEX/shares outstanding(2) Tax Adjusted EBIT / Total Debt + Equity

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ROIC(2)

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Capital Structure

Fourth Quarter 2008 Key Financial MetricsLiquidity $382 millionFinancial Leverage 3.1xInterest Coverage 7.4xFixed Rate/ Total Debt 57%Weighted Interest Rate 3%

($Millions)Outstanding at

December 31, 2008 MaturityAR Securitization $295 2010Inventory Revolver $198 2013Real Estate Mortgage $42 2013High Yield Bonds $150 2017Convertible Bonds $450 2025 / 2026Other $6 N/A

Total Debt $1,141

WESCO – A Solid Foundation

…bigger, more diversified, more profitable with a stronger capital structure

2008 2001 - 2003 (Average)

Better End Market Diversification Industrial 40% Industrial 42%Construction 25% Construction 37%Data Communications 13% Utility 15%Utility 16% CIG 6%CIG 6%

Improved Operating Margins 5.7% 2.5%

Seven Accretive Acquisitions $1+ B Sales N/A$1.00 + EPS

LEAN - Continuous Improvement Launched Spring 2003 N/A

Experienced Management Team Improved Good

Excellent IT System Capabilities Enhanced Good

Solid Capital Structure 3.1x 5.5x Leverage

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How is WESCO different from the last downturn?

Deliver organic sales performance greater than the industry supplemented with accretive acquisitions

Protect operating margins

Provide superior return on invested capital

Manage financial leverage

Financial Objectives

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Market leader with low business risk profile

Organic sales growth faster than market

Proven business model uniquely positioned in large, fragmented growth market

Solid ROIC performance

Proven acquirer

Low cost operator with LEAN mentality

Invest in WESCO

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