The prefecture of Kastoria is situated in the western end of West Macedonia. It is adjacent on the north with the prefecture of Florina, on the south, east and south-east with the prefectures of Grevena and Kozani, on the south-west with the prefecture of Ioannina and on the west with Albania.

The soil of the region is mountainous and the climate is continental with cold winters and hot summers. The temperature presents great variations between winter and summer, and during winter it is often below zero so the lake waters are frozen. According to the latest census the population of Kastoria comes up to 51.934 inhabitants.