This work is focused on the analysis of light conditions in spruce natural forest using hemispherical images in NNR Poľana. One of the main conditions for the successful formation and outgrowth of natural regeneration is sufficient amount of radiation under the main forest stand level or below the canopy layer. The analysis of light conditions was performed by indirect method of measuring relative radiation based on the analysis of hemispherical images. Hemispherical photography and research were performed on the circular areas with diameter of 17.8 m (1 000 m2). There was established a line of photography points with spacing of 5 m on every circular area. Totally, 91 hemispherical images were evaluated. We analysed the variability of radiation on every measuring point, areas and height level in the natural forest. The results showed that all parameters of relative radiation had significantly higher average values in higher height level. However, the overall variability of radiation was the same in both height levels. The variability of radiation at the level of all measuring areas (average values for 1000 m2) was lower in lower height level and the differences on neighboring areas were smaller. The variation range of average values in higher level was 15%, in lower level 11%. The correlation between parameters of radiation and forest stand characteristics describing spruce forest stand dividing on two level was not statistically significant (the correlation coefficient only randomly differs from zero). In the case of merging all areas in one set, the correlation was statistically significant. The intensity of radiation evaluated on the basis of all parameters decreases with increasing circular base and stand stock. Generally, there is very low effect of forest stand characteristics and the amount of variability of radiation.