OSISKO MINING CORPORATION ANNOUNCES THE EXERCISE OF THE OVER-ALLOTMENT OPTION

THIS NEWS RELEASE IS INTENDED FOR DISTRIBUTION IN CANADA ONLY AND IS NOT AUTHORIZED FOR DISTRIBUTION TO UNITED STATES NEWSWIRE SERVICES OR FOR DISSEMINATION IN THE UNITED STATES.

(Montreal, February 23, 2009) Osisko Mining Corporation (“Osisko” or the “Corporation”) (OSK:TSX, EWX: Deutsche Boerse) announces that, in connection with its previously announced public offering of 77,000,000 units (the “Units”) of the Corporation at a price of $4.55 per Unit, the syndicate of underwriters (the “Underwriters”), led by Thomas Weisel Partners Canada Inc. and BMO Capital Markets, have notified the Corporation that they are exercising the option (the "Over-allotment Option") to purchase an additional 15% of the Units for market stabilization and over-allotment purposes. The Underwriters will thereby purchase 11,550,000 additional Units (the “Additional Units”) at a price of $4.55 per Additional Unit.

The exercise of the Over-allotment Option will increase the gross proceeds received from the offering by $52,552,500 to a total amount of $402,902,500. The Corporation intends to use the proceeds of the offering for the development and construction of its Canadian Malartic Project and for working capital purposes.

The securities offered have not been registered under the U.S. Securities Act of 1933, as amended, and may not be offered or sold within the United States or to, or for the account or benefit of, U.S. persons absent registration or an applicable exemption from the registration requirements. This release shall not constitute an offer to sell or the solicitation of an offer to buy securities in the United States nor shall there be any sale of the securities in any State in which such offer, solicitation or sale would be unlawful.