This paper describes the microtoponyms of the south-eastern part of the Beskid Niski region, which before World War II was inhabited mainly by Lemkos and Poles. In spite of the fact that the examined area lies on the border of Poland and Slovakia, in this paper it is treated as an internal borderland, mainly between a nation (Poles) and an ethnic community that is not a nation (Lemkos). The microtoponyms collected during the research are interpreted as linguistic signs revealing phenomena and processes connected with the coexistence of groups of people who differ in language, culture and religion. In this paper selected issues concerning microtoponyms as symptoms of ethno-linguistic, religious and socio-cultural borderlands are discussed successively.