This diploma thesis is dedicated to the old-growth mountain forests. Subject of examination was spruce forest, situated in NNR Poľana territory. The data used for the analysis were measured on the PRP (permanent research plot) network located in the stands 526 and 527, namely the 6 highest plots of 1 000 m2, at an altitude over 1,400 m. In our thesis we compared condition stand between years 2013 and 2018. Issue of thesis is general characteristic of the Picea abies species, but we also drew attention on most common causes of spruce stands necrosis. Because of adverse climate change and spreading of pathogens associated with it, we must point our view on natural alpine forests and use them as a model of Pro silva cultivation. The aim of thesis was to analyze condition of natural spruce forest, using calculated dendrometric characteristics and assess their subsequent development. For the calculations shown in the results we used data obtained by direct measurement on PRP 1-6. Then we calculated dendrometric quantities characterizing the state and production of the natural forest. We described variability of characteristics in order to estimate their future development. Between 2013 and 2018 we compared the change in the thickness structure of individuals over 8 cm. The data from 2018 we also used to make graphs of stand height structure. The results show that, despite the fact that the research site is a spruce primeval forest, it is heading towards a small-scale old-growth forest texture. This is due to the following features: the representation of all stages of the development cycle of natural forests, the alternation of areas with different thickness and height structure, a small tendency to verticalization of the stand and the disintegration of the upper layer by the death of individual trees, or a group of trees. Considering that, the research object in the NNR Poľana may serve as a model for the management in similar stands.