The aim of the study is to present the results of determination of radioactivity of artificial ^{137}Cs and natural ^{40}K and certain heavy metals in soil samples collected from the eastern part of the Main Ridge of Carpathians, including the Beskid Niski Mts and the Bieszczady Mts. The evaluation of level of radionuclides was based on the bulk density analysis of the soil. A valuable finding of the study was a good linear correlation between the level of ^{137}Cs concentration and bulk density of the soil as well as an inverse correlation between radioactivity of natural ^{40}K and tested soil density. This might indicate though a high competitiveness of these elements between each other. Moreover, a good correlation between the concentrations of artificial element ^{137}Cs and Pb has been also observed in soil samples collected from the Beskid Niski Mts. In most cases, the level of artificial ^{137}Cs was lower comparing to an average ^{137}Cs concentration established for soils in Poland.