John M. Flood, 49, a former president of the Flood Pontiac Company and a lifelong resident of the Washington area, died Saturday at Suburban Hospital in Bethesda following a heart attack.

Mr. Flood, who lived in Chevy Chase, was born in Washington and graduated from Sidwel Friends School here. Following his graduation from Gettysburg College in Gettysburg, Pa., he joined Flood Pontiac, which had been started by his father, Everett Flood, in 1933. After Everett Flood's death in 1971, John Flood became president of the firm. He continued in that position until January 1980, when the company closed.

Since then, Mr. Flood had been associated with Town and Country Properities, Inc.

He was a former member of the board of directors of the Automotive Trade Association of the National Capital Area.

He also was a member fo the Justice Columbo Masonic Lodge No. 3, the Wesley Methodist Church and the Columbia Country Club. He was an amateur photographer and a stamp collector.

Survivors include his wife, Jane, and two sons, Micahel and Mark, of Chevy Chase; his mother, Dorothy Flood, one brother, Paul, and one sister, Ellen Talbott, all of Chevy Chase, and one grandfather, Maynard Flood, of Tuscon, Ariz.

The family suggests that expressions of sympathy be in the form of contributions to the Children's Hospital National Medical Center, Washington, D.C.