The capital of the regional unit is the town of Chios.

The regional unit consists of the islands of Chios, Psara, Oinousses and some smaller uninhabited islands (including Antipsara), all in the Aegean Sea.

The regional unit Chios is subdivided into 3 municipalities.

These are (number as in the map in the infobox):[2] As a part of the 2011 Kallikratis government reform, the regional unit Chios was created out of the former prefecture Chios (Greek: Νομός Χὶου).

The prefecture had the same territory as the present regional unit.