NATION

J. Walter Thompson Co., one of the world’s largest advertising agencies, and its affiliated public relations company, Hill & Knowlton Inc., will both have new chief executives, the companies announced.

Joseph W. O’Donnell, 43, was elected as chief executive of J. Walter Thompson, succeeding Don Johnston in that post.

In addition, O’Donnell was designated to succeed Johnston as chairman of the advertising unit after Johnston leaves that position effective Dec. 31.

While stepping down at the advertising subsidiary, the 59-year-old Johnston remains as chairman and chief executive of JWT Group Inc., the parent of both J. Walter Thompson and Hill & Knowlton. Johnston had been chief executive at J. Walter Thompson since 1974 and chairman since 1978.

Robert L. Dilenschneider, 42, was elected president and chief executive of Hill & Knowlton. He succeeds Loet A. Velmans, 63, who remains chairman of the public relations firm.