Wanna run a foundation?

Not one of those tiny trusts someone's rich aunt left behind to cultivate petunias and flower gardens. But a huge fund worth hundreds of millions of dollars, with projects around the world and a name easily recognized in nearly any language.

The Rockefeller Foundation is looking for a president. In the past, you had to know someone just to have your name breathed to the trustees of this august group. Now you can apply yourself, or get a friend to submit your nomination.

Just clip the ad running this week in The Washington Post, New York Times and Economist Magazine of London, and write to Rev. Theodore Hesburgh, chairman of the foundation's search committee. Enclose a resume and references. No box tops necessary.

The foundation post has been vacant since March when cancer unexpectedly took the life of Dr. John Knowles, 52 onetime general director of Massachusetts General Hospital in Boston and an outspoken member of the medical profession. Knowles was elected president of the Rockeffeller Foundation in 1972.

The foundation's search committee has been soliciting recommendations from the usual sources-mostly its own staff and the Establishment grapevine. But this time, for the first time, it decided to go public.

"We want to make as broad a search as possible,c explained Henry Romney, spokesman for the $750 million foundation, which ranks among the nation's five largest. "Besides, it's the temper of the times."

In fact, the 66-year-old Rockefeller Foundation is only the latest in a string of dignified organizations that have been turning to the Help Wanted to find new leadership.

Whether the ad campaigns have actually been taken seriously by the selection committees-or have served simply as publicity exercises-has been the subject of some debate. The Ford Foundation, for instance, recently advertised for a new chief in a half-dozen national papers, only to name Franklin Thomas, a lawyer who was already sitting on the foundation's board.

By the way, neither the Ford nor the Rockfeller ads listed what the requirements were for their top jobs-a fact which officials at both foundations attributed to the difficulty in describing just what a foundation president does.

"It's really not written anywhere," said Romney.