BOSTON — Former CVS Caremark chief executive officer Tom Ryan has joined the private equity firm Advent International as an operating partner.

Advent executives say Ryan will advise and work closely with the firm’s investment professionals to identify attractive opportunities and generate post-investment value at retail and health care companies around the globe.

“Tom is simply one of the world’s top corporate leaders,” Advent managing partner David Mussafer says. “He is a great addition to Advent, and we look forward to working with him to identify and develop investment opportunities.”

Ryan joined CVS in 1974 as a pharmacist and became chief executive officer in 1994. He retired last year.

He oversaw CVS’ 2007 $21 billion acquisition of Caremark RX, a move that transformed the company from a drug store chain in the Northeast to a diversified pharmacy services company with more than $100 billion in annual revenue.