Former Equity Office head Timothy Callahan has been named president and CEO of Trizec Properties Inc., in an appointment effective immediately. Callahan replaces Christopher Mackenzie, who resigned from his post to pursue other interests.

The New York-based REIT also named Casey Wold, currently chief investment officer, as chief operating officer.

Callahan was president and CEO of Equity Office Properties Trust from 1996 through April of this year. Before joining Equity Office, he had served since 1992 as executive vice president of Equity Group Investments Inc., where he was responsible for coordinating financing and capital markets activities.

Wold has been with Trizec since 1995, and will continue to serve as CIO, responsible for Trizec’s investment and portfolio strategy. He also previously served was president of TrizecHahn Office Properties, formerly the U.S.-based subsidiary of Trizec Corp.

Both executives will be members of Trizec’s board of directors.