The article discusses problems connected with Balto-Slavic mythological parallels, including typology of mythological characters, lexical similarities resulting from genetic affinity and borrowing, as well as the influence of mythological systems of neighbouring peoples. Some new Balto-Slavic parallels have been suggested, viz. Rugių boba – Baba Ruga (Roga); Pikulas – pikulík; nelabais, and nelabasis – nelapši, nelapszy, with the focus on their ethnolinguistic aspect, both as mythological characters and as elements of the mythological lexicon. Special attention has been paid to the etymology of these words. The new parallels between the two groups of related languages provides additional material related to Slavic and Baltic ethno- and glottogeny.