Mary M. Dowell, 67, a cancer patient who took part in conferences with doctors and other cancer patients to help them understand better how to cope with the illness, died Friday at Walter Reed Army Medical Center of acute respiratory and renal failure.

Mrs. Dowell, a resident of Silver Spring, became ill with cancer in 1970, and underwent surgery and other treatment. She was pronounced cured. In 1973, she was afflicted with another type of cancer and again recovered.

Under the auspices of Walter Reed, she volunteered to attend conferences of doctors to discuss her experiences with the illness. She also met with numerous patients to tell how she had coped with cancer.

Mr. Dowell was born in Philadelphia and grew up there. She moved to Washington in the early 1930s and went to work for the old War Department.

She married Col. Cassius M. Dowell here and accompanied him to the Phillipines, where he served on the staff of Gen. Douglas MacArthur before World War II. Later, she accompanied her husband, a noted military lawyer, to Fort Niagara, N.Y., and Camp Dix (now Fort Dix), N.J. Col. Dowell retired from the Army in 1944 and the family moved to Cincinnati.

In 1949, they moved to Washington. Col. Dowell died in 1957.

Survivors include a son, Richard P., of Alexandria; her mother, Sarah McHenry, of Ventnor City, N.J.; three brothers, James McHenry, of Hyattsville, Joseph McHenry, of Vienna, and William McHenry, of Severn, Md., and three sisters, Mrs. Harold Mitchell, of Adelphi, Mrs. John Sumner, of Silver Spring, and Mrs. Robert DiPiano, of Ventnor City.

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