The (Greek Islands) Islands of Greece are seven Groups
The regios and locations are the followings links :

The Northeastern Aegean Islands:
Agios Efstratios, Thasos, Ikaria, Lesvos, Limnos,
 Inousses, Samos, Samothrace, Chios, Psara.
http://www.travelpage.gr/greece/North-Eastern_Aegean_Islands.htm

The Sporades:
Alonissos, Skiathos, Skopelos, Skyros  ,Evia
http://www.travelpage.gr/greece/Evia_and_the_Sporades.htm


Argo-Saronic Islands:
Angistri, Aegina, Poros, Salamina, Spetses, Hydra and the
 coastal area of Methana.
http://www.travelpage.gr/greece/Saronic_Islands.htm

The Cyclades:
A group of 56 islands, its most important ones being Amorgos, Anafi,
Andros, Antiparos, Delos, Ios, Kea, Kimolos, Kythnos, Milos, Mykonos, Naxos, Paros,
 Santorini, Serifos, Sikinos, Sifnos, Syros, Tinos, Folegandros, as well as the “Minor
 Cyclades” comprising Donousa, Irakleia, Koufonisia and Schinoussa.
http://www.travelpage.gr/greece/Cyclades.htm

The Dodecanese:
Astypalaia, Kalymnos, Karpathos, Thasos, Kastelorizo, Kos, Lipsi,
Leros, Nisyros, Patmos, Rhodes, Symi, Tilos, Halki.
http://www.travelpage.gr/greece/Dodecanese.htm

Crete :
Heraklion,Chania,Lasithi and Retymno
http://www.travelpage.gr/greece/Crete.htm

The Ionian Islands:
The Ionian Sea is home to one sole island group:
Zakynthos, Ithaca, Corfu, Cephallonia, Lefkada, Paxi, Antipaxi,
Ereikoussa, Mathraki, Meganissi, Othoni, Strofades.
These islands, together with Kythira, which is however cut-off from the rest, opposite
 the southern Peloponnese (Lakonia), as well as neighbouring Antikythira, they
constitute the Eptanissa
http://www.travelpage.gr/greece/Ionian_Islands.htm