Mary C. Seybold, 79, who was active in service organizations and was the wife of a former governor of the Panama Canal Zone, died of cancer Tuesday at Walter Reed Army Hospital.

She accompanied her husband, John S. Seybold, to the Canal Zone when he was stationed there as a 2nd lieutenant, and again when he was a major general and governor of the zone in the mid-1950s. Gen. Seybold retired from the Army in 1956, and they had lived in Washington since then.

During her years as an Army wife, Mrs. Seybold took an active part in social activities related to the Corps of Engineers, in which her husband was an officer. A notable instance was the establishment of Riverdale, N.D., in connection with the construction of the Garrison Dam on the Missouri River. During World War II, Mrs. Seybold was a member of the Red Cross Motor Corps.

At the time of her death, she was a member of the Salvation Army Auxiliary and the Sulgrave Club.

In addition to her husband, of the home in Washington, survivors include a sister, Mrs. Herbert A. Marshall, of Topeka, Kan., where Mrs. Seybold was born and grew up, and two grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the Army Distaff Foundation.