Sponsored Topics. Columbiana is a city in Columbiana and Mahoning Counties in the U.S. state of Ohio. The population was 5,635 at the 2000 census. The Columbiana County portion of Columbiana is part of the East Liverpool–Salem Micropolitan Statistical Area, while the Mahoning County portion is part of the Youngstown–Warren–Boardman, OH-PA Metropolitan Statistical Area.