The present study focuses on seals of known provenance that are related to the coasts of the Adriatic and the Ionian Sea, with the exception of Sicily. A corpus of sixty-three seals was formed, dating mainly between the ninth and the eleventh centuries. It can be divided into two categories: seals found in the area under consideration (thirty specimens) and seals that originated from the Adriatic, but were found outside its limits (thirty-three specimens). On the basis of this evidence, the study comments on the circulation of seals, the trends observed in that respect and their conformity to the principle of territoriality, according to which seals tend to be found within, or in the vicinity of, the area in which they were issued. This principle, which seems to be prevalent to the rest of the empire, is not applied catholically in the case of the Adriatic, since the eastern, Balkan rim diverges from it. If this is not a consequence of the lack of published material, then perhaps it can be attributed to the significance of this region as a frontier zone in the periphery of Byzantium, linking the Italian possessions to the centre.