They were introduced as part of the "Kallikratis" administrative reform on 1 January 2011 and are comparable in area and, in the mainland, coterminous with the pre-"Kallikratis" prefectures of Greece.
Foron introducidos como parte da reforma administrativa Kallikratis do 1 de xaneiro de 2011 e son comparables en tamaño e, na parte continental, lindeiras coas prefecturas de Grecia pre-"Kallikratis".