-By Steve McClellan

ORLANDO, FLA. Dennis Donlin, general manager of GM Planworks, the unit of Publicis Groupe's Starcom MediaVest Group that handles media planning and buying on General Motors' $3 billion-plus annual ad account, is leaving the agency effective April 1, the shop said today.

Donlin has been with Planworks since its inception in 2000, when it won GM's planning assignment, and he oversaw its successful pitch in 2005 to win buying chores as well. (The shop was named Adweek's U.S. Media Agency of the Year for its performance in '05.)

SMG said a successor would be named this week or next.

In a statement, Donlin cited both career and personal reasons for his departure: "It is simply the right time for me to take stock and consider my next career move, and I want to do that while spending more quality time with my kids, the youngest of which graduates from high school next year."

"Dennis has been an integral part of our Planworks operation and a big part of the success that division has achieved," said SMG CEO Laura Desmond in a statement. "We wish him the very best in his future endeavors."

Donlin began his career in in 1979 when he joined DMB&B, and he ultimately became part of Televest and then MediaVest as the media services unit separated and evolved. He has led the Planworks operation in Detroit since 2000.