As the market for office space shows signs of recovery, the suburbs are getting left behind.

For decades, the suburbs benefited from companies seeking lower rent, less crime and a shorter commute for many workers. But now, office buildings in many city downtowns have stopped losing tenants or are filling up again even as the office space in the surrounding suburbs continues to empty, a challenge to the post-war trend in the American workplace and a sign of the economic recovery's uneven geography.

Even...