Analyses of nucleotide sequences of 5’- and 3’- ends of mitochondrial cytochrome oxidase subunit I (5’COI, 3’COI) and fragments of internal transcribed spacer 2 (ITS2) of nuclear rDNA gene confirmed the status of Stagnicola corvus (Gmelin), Lymnaea stagnalis L. and Ladislavella terebra (Westerlund) as separate species. The same results showed that Stagnicola palustris (O. F. Müll.) and S. turricula (Held) could also be treated as separate species, but compared to the aforementioned lymnaeids, the differences in the analysed sequences between them were much smaller, although clearly recognisable. In each case they were also larger than the differences between these molecular features of specimens from different localities of S. palustris or S. turricula. New data on the distribution of S. palustris and S. turricula in Poland showed – in contrast to the earlier reports – that their ranges overlapped. This sympatric distribution together with the small but clearly marked differences in molecular features as well as with differences in the male genitalia between S. palustris and S. turricula strongly support the view that they are separate species and not two subspecies within S. palustris.