Fay G. (Pat) Ewing, 61, a Northern Virginia real estate agent and a former president of the Greater Falls Church Republican Women's Club, died of cancer Thursday at Fairfax Hospital.

Mrs. Ewing had lived in Falls Church since 1968 and had worked in the McLean office of the Better Homes Realty for the last 10 years.

She was a native of La Crosse, Wis., asd graduated from the University of Wisconsin. She came to Washington during World War Ii and was an analyst with the Office of Strategic Services and the War and State departments.

In 1950, she married Donald F. Ewing, a Foreign Sevice officer, and accompanied him to posts in Morocco, Greece, Madagascar and Thailand.

Mrs. Ewing was president of the Greater Falls Church Republican Women's Club in the late 1970s. She also was a member of the Women's Club of Falls Church.

In addition to her husband, of Falls Church, survivors include a son, Donald F. Jr. of Penascolsa, Fla.; a stepson, David Ewing of Tokyo; a stepdaughter, Joanna Jones of Bath, Me.: a sister, Joan Seig of Santa Fe, N.M., and seven grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society.