In this work we deal with snow cover, the influence of forest in relation to snow cover, and the influence of winter in relation to roe deer. In first part we process scientific literature dealing with snow cover, its formation and interaction with the forest. We also deal with the effect of temperature and snow on the Roe deer (Capreolus capreolus) throught the winter season. The impact of the forest on the snow cover was evaluated for the BR Poľana area, for the winter period 2017 to 2020. The values of the snow cover parameters were the highest in the open area and decreased with the thickening of the canopy. The parameters were also affected by the exposure of the research areas and by altitude. The influence of winter season on roe deer survival was expressed by the winter severity index - WSI. The parameters for its calculation were the minimum daily temperatures and snow depths. These were provided by three weather stations, each one at different altitudes in the Poľana area, in the winter period from 2003 to 2020. The results show the effect of altitude on the winter survival of roe deer. At lower altitudes, conditions are more favourable, while conditions worsen as altitude increases.