John P. Meshkoff, 78, a retired Metropolitan Police detective who served for 17 years on the special investigations squad and who was a founder of the Police Boys Club, died Tuesday at Fairfax Hospital following an aneurism. He lived in Great Falls, Va.

Mr. Meshkoff joined the police department in 1930 and began his career as an instructor at the Police Academy. In 1934, he helped found the Police Boys Club and served as its first director for four years. He also played a key role in establishing its summer camp.

Four years later, Mr. Meshkoff transferred to the special investigations squad, where his duties included probing subversive activities and helping to set up security measures for public officials and visiting dignitaries. He received numerous commendations before his retirement in 1955.

From 1964 until a second retirement in 1974, Mr. Meshkoff did investigative work for the Army Corps of Engineers.

He was born in Migelow, Russia. He came to this country with his family a boy and lived in Chicago and Rockford, Ill. He attended Northwestern University and the American College of Physcial Education in Chicago.

Mr. Meshkoff taught at the elementary school level in Chicago in 1925-26 and then joined the Marine Corps. He saw duty in Nicaragua during the U.S. intervention there and later was an instructor at Parris Island, S.C. He joined the police department in Washington after leaving the Marine Corps.

He was a member of Kemper Lodge of the Masons, the Scottish Rite and the Kena Temple of the Shrine.He belonged to the Veterans of Foreign Wars Post No. 9274 and the Marine Corps League.

He survived by his wife, Olivia R., of Great Falls; a son, John P. II, of San Francisco; two daughters, Janice E., of Santa Monica, Calif., and Pamela Renfro, of Meadow Vista, Calif., three sisters, Eugenia Wynot, of Manchester, N.H., Alexandra Morgan, of Baltimore, and Elaine Testor, of Weston, Conn.; a brother, Peter, of Riverside, Calif., and one grandchild.

The family suggests that expressions of sympathy be in the form of contributions to the Great Falls Episcopal Church Building Fund.