The contents of artificial and natural radionuclides of 137Cs, 90Sr, 226Ra, 232Th, and 40K had been investigated in muscle and bone tissues, gill petals, and scales of common perch Perca fluviatilis and pikeperch Sander lucioperca from two fishing areas of the Dnipro (Zaporizhzhia) Reservoir. The specific radionuclide activities were measured with the SEG-001 “AKP-C” and SEB-01-150 scintillation spectrometers of gammaand beta-radiation energy in Bq/kg of wet weight. The radioactive elements of both natural and artificial origins were concentrated greatly in common perch tissues compared to pikeperch. The bone and muscle tissues contained the maximal levels of radionuclides, while respectively smaller amounts of radionuclides were found in gills and scales. The radionuclide levels in the tissues of investigated fish species were significantly higher in the Dnipro Reservoir area with weak flowage and slow water exchange.