Soil organic matter is a complex, heterogeneous set of organic substances of different origins, differing in age, molecular structure, stability, variable composition, varying degrees of dispersion, activity, and thus in relationship to other soil matter components or living organisms. It plays a central role in soil fertility and the functioning of ecosystems and can be a more sensitive indicator of changing environmental conditions than other physical and physico-chemical properties of soil. The aim of the work was: 1/ to assess the differences in carbon and nitrogen concentration between the localities in the National Nature Reserves Jánošíková kolkáreň, Smrekovica, Ďumbier and Pilsko, 2/ to assess the effect of spatial and altitude factors, and 3/ to evaluate the dependence of carbon and nitrogen concentration on the content of skeleton, pH, and the stand structure. In general, it can be stated that the highest average carbon concentration was found on Ďumbier with a value of 15.13% at the soil depth of 0 ˗ 30 cm, and the lowest on the territory of Pilsko with a value of 6.02%. Among the studied abiotic factors, the elevation, slope, and skeleton content showed the most important effect on the concentrations of carbon and nitrogen, or C/N ratio. Conversely, an aspect only slightly affects observed parameters. Furthermore, we can state that on the one hand, with increasing depth of soil, the effect of altitude and pH of the soil rises too, but on the other hand, the effect of slope decreases. The increase in the total number of trees was also reflected in the increase of carbon and nitrogen concentrations, a significant effect can be observed especially in the case of trees with a thickness of 32 ˗ 44 cm.