The exact date of the theme's establishment is unclear; a "strategos" of Dyrrhachium is attested in the "Taktikon Uspensky" of , but several seals of "strategoi" dating from the previous decades survive. J.B. Bury proposed its creation alongside the themes of the Peloponnese and Cephallenia in the early 9th century, with the historian Jadran Ferluga putting the date of its establishment in the reign of Emperor Nikephoros I (). Its boundaries are not very clear. To the north, it abutted the Theme of Dalmatia and the Serbian principality of Duklja, and the Theme of Nicopolis to the south. The theme covered the coast in between, but how far inland it extended is uncertain: according to Konstantin Jireček, it reached as far as Drivast and Pulati in the north, and Berat in the centre, and bordered the Slav-inhabited lands of the Upper Devoll and Ohrid in the south. During the Byzantine–Bulgarian wars of the late 10th and early 11th centuries, the city seems to have been autonomous or at times under Bulgarian suzerainty.