Theodore L. Miazga, 59, a lawyer and former judge in Prince George's County as well as a former member of the county planning board, died Tuesday at Leland Hospital in Riverdale following a heart attack.

Following World War II service in the Army Air Corps, Mr. Miazga earned a law degree from George Washington University Law School. He then practiced law in Riverdale with his sister, Matilda, for more than 25 years.

In 1951, he became one of Prince George's County's trial Magistrate Court judge and also served as a Police Court judge, presiding in Hyattsville.

In 1967, Mr. Miazga was named to the Prince George's County. Planning Board of the Maryland-National Capital Park and Planning Construction, which advises on zoning matters in the county.

He was one of the organizers of the Prince George's County Beautification Committee and helped start the county street tree planting program and the Park and Planning Commission's memorial tree planting program.

Survivors include his wife, Viola, a son, Theodore J., and a daughter, Janina, all of the home in University Park; a brother, Leo, of Frederick County, Md.; and four sisters, Mary Shonk, of Wyandotte, Mich., Helen Cogswell, of Phillip, N.J., Margaret Kalie, of Shickshinny, Pa., and Matilda Miazga, of Hyattsville.