The study was carried out on 9 species of freshwater bivalves (Dreissena polymorpha, D. bugensis, Unio crassus, U. pictorum, U. tumidus, Anodonta anatina, A. cygnea, A. woodiana, and Pseudanodonta complanata). The mitochondrial COI gene studied with PCR-RFLP and 6 restriction enzymes (ScrFI, Csp6I, BsiZI, EcoRI, BamHI and AluI) showed the absence of individual variability within each species studied. The genetic variability of the COI involved differences at the species, genus, and family level, depending on the restriction enzyme used. Four restriction enzymes (ScrFI, Csp6I, BsiZI and AluI) proved efficient in differentiating between D. polymorpha and D. bugensis as well as in identifying the three Unio species (Csp6I and AluI), U. crassus, and P. complanata (ScrFI and AluI). EcoRI and AluI made it possible to identify A. anatina and P. complanata. Two (for EcoRI), 3 (for Csp6I, BsiZI), 5 (for ScrFI) and 9 (for AluI) unique genotypes that occurred in a single species each were observed; the enzymes may therefore be regarded as species-specific markers. Only restriction enzyme AluI can differentiate between A. cygnea and A. woodiana.