The area of Lithuania Minor embraced the land between the lower reaches of the river Dangė () to the north and the major headstreams of the river Prieglius (, now Pregolya) to the south. The southwestern line ran from the Curonian Lagoon () along the Deimena River to its south, continued along the Prieglius River to the Alna (now Lava) river, up to the town of Alna and hence southward along the Ašvinė (Swine) river to Lake Ašvinis () and from there eastward to the border of Lithuania Major. The region embraced about 11 400 km². The broader understanding of Lithuania Minor includes the area west from the Alna and south form the lower reaches of the Prieglius and the Sambian Peninsula, making up 17–18 thousand km2 in total.