Mr. Kim, 37, chose to form a new company, Bright Sun.
"We're going to fill the gap between traditional advertising agencies and traditional consult- ing companies," he said.
In a fast-rising career at J. Walter Thompson Co., Mr. Kim built a reputation as one of the industry's sharpest young minds. Interpublic Group of Cos. hired him as director of strategic planning and, three years ago, Interpublic's McCann brought him on board as vice chairman-chief strategy officer.
His mission, said Chairman-CEO John Dooner, was to change the agency's focus from managing accounts to building brands through great ideas. In the past year, Mr. Kim began to focus on the Fourteenth Floor, an in-house strategic consultancy he founded.
an incredibly difficult separation," Mr. Kim said of his decision to leave. "It's more about conflicting beliefs and values than anything else. John was incredibly tolerant, but in the end my vision pushes the edge of the envelope further than he's willing or able to go."
A McCann spokesman said: "Peter's departure had nothing to do with a difference in vision; it had to do with tactics and practices."
Bright Sun's aim will be to solve deep-seated business problems through a combination of strategic, intellectual and creative resources.
"Most companies don't have advertising or marketing problems," Mr. Kim said. "They have much more fundamental problems that usually can only be solved by a better understanding of what business they're in. You know, Nike's not in the shoe business. It's really in the 'pursue your passion' business."
Bright Sun probably won't create ads in-house, but might find producers and talent who will or conduct agency searches on behalf of clients.
There are no clients yet, but Mr. Kim has leased space in midtown Manhattan and