New York

Menlo Park

Washington DC

London

Paris

Madrid

Tokyo

Beijing

Hong Kong

Davis Polk & Wardwell LLP

450 Lexington Avenue

New York, NY 10017

June 18, 2010

MSCI Inc.

88 Pine Street

New York, NY 10005

(212) 804-3990

Ladies and Gentlemen:

We have acted as special counsel for MSCI Inc. (the “Company”) in connection with the filing of a Registration Statement on Form S-8 under the Securities Act of 1933, as amended, relating to 3,060,090 shares (the “Shares”) of the Company’s Class A common stock, par value $0.01 per share, deliverable pursuant to the RiskMetrics Group, Inc. 2007 Omnibus Incentive Compensation Plan (the “Plan”).

We have examined such documents and such matters of fact and law as we have deemed necessary for the purposes of rendering the opinion expressed herein.

Upon the basis of the foregoing, we are of the opinion that the Shares deliverable pursuant to the Plan have been duly authorized and, when and to the extent issued pursuant to the terms of the Plan, will be validly issued, fully paid and nonassessable.

We consent to the filing of this opinion as an exhibit to the Registration Statement.

Very truly yours,

/s/ Davis Polk & Wardwell

Davis Polk & Wardwell LLP