Addison is a borough in Somerset County, Pennsylvania, United States. It is part of the Johnstown, Pennsylvania Metropolitan Statistical Area. The population was 214 at the 2000 census.
Addison is located at 39°44′43″N 79°19′59″W / 39.74528°N 79.33306°W / 39.74528; -79.33306 (39.7472, -79.3331), about 30 miles (48 km) WNW of Cumberland, Maryland and about 30 miles (48 km) ENE of Morgantown, West Virginia. According to the United States Census Bureau, the borough has a total area of 0.6 square miles (1.6 km2), all land.
As of the census of 2000, there were 214 people, 87 households, and 54 families residing in the borough. The population density was 380.4 people per square mile (147.5/km²). There were 96 housing units at an average density of 170.6 per square mile (66.2/km²). The racial makeup of the borough was 100.00% White.