NEW YORK — Sara Lee Corp. said Tuesday that Cornelis Boonstra, who became president of the company only six months ago, has retired.

The company said that Boonstra, a 55-year-old executive who has been with the firm for 20 years, was retiring for personal reasons. A spokeswoman for the company said she could not elaborate. Boonstra could not be reached for comment.

His retirement was effective Dec. 31, the company said. In addition to leaving the post of president, Boonstra also retired as chief operating officer and as a director.

It is expected, however, that Boonstra will continue his association with the firm by being named to the supervisory board of Sara Lee/DE, a Dutch entity that oversees a large portion of the corporation’s businesses, including most of its international operations. This is expected to happen in the fall, the spokeswoman said.

Boonstra, a Dutch citizen, joined Sara Lee in 1974 as general manager of its Intradel division in the Netherlands. He became executive vice president in 1988, with responsibility for the company’s coffee, grocery, household and personal care businesses. He continued to be based in the Netherlands until moving to Chicago, Sara Lee’s headquarters city, when he assumed the presidency last July.

Boonstra’s duties will be absorbed by two corporate senior vice presidents. They are Donald J. Franceschini, 57, who is chief executive officer of the Sara Lee Intimates division and director of the Personal Products division in Europe, and C. Steve McMillan, 47, president of Sara Lee’s worldwide food operations, as well as its household and personal care and Sara Lee/DE businesses. Franceschini and McMillan will report to John H. Bryan, chairman and ceo of Sara Lee Corp., with Franceschini directing the corporation’s Personal Products operations and McMillan overseeing the household and personal care lines of business and the packaged meats, bakery, coffee and grocery operations worldwide.

With his expanded responsibilities, Franceschini will oversee a complex of international apparel and accessories businesses that posted a volume of $6.1 billion in the fiscal year ended July 3, 1993.

In addition to its intimate apparel business, which features such names as Playtex and Bali, the personal products group includes Sara Lee Hosiery, maker of the Hanes and L’eggs brands; the knitwear division, which makes men’s and women’s underwear, casualwear and activewear under the Hanes, Hanes Her Way and Champion labels, and the Aris Isotoner and Coach accessories lines.

Bryan, in a statement, noted that Boonstra “leaves a very important legacy to the corporation,” having been one of the “major figures in the development of our international presence.”

Analysts generally concurred that Boonstra’s exit most likely was based on a desire to change his lifestyle.

Les Pugh, of Salomon Bros., said, “He’s spent the last six months traveling a lot more, and he also moved to Chicago. I think it was a genuine lifestyle decision and he thought, ‘I don’t need to do this anymore.”‘

“I think he left truly for personal reasons,” said Joanna Scharf of S.G. Warburg. “He’s an extremely good operations manager with an aggressive American style. He left of his own volition, and it’s a loss to the firm.”

Ronald B. Morrow, an analyst for Smith Barney Shearson, said: “He got along famously with John Bryan for the 16 years they worked together. It wasn’t a blowup between him and Bryan.”