Background: Snow is known to have a major impact on the distribution of plants in arctic and alpine ecosystems; however, its impact on understorey vegetation in boreal forests is little reported. Aims: To study the effects of trees on the distribution of snow and examine the small-scale spatial relation between snow distribution and ground vegetation. Methods: Detailed spatial variation in snow depth and summer precipitation, canopy dimensions and locations of individual trees, and ground vegetation cover were observed in a coniferous forest, and the spatial correlations between these variables were examined. Results: Spatial patterns of snow remained unchanged throughout the winter and across two different winters. Snow depth showed significant correlations with different tree influence indices calculated based on the distance to the trunk, height, diameter or canopy extent. Dwarf shrub cover correlated positively with snow, and moss cover correlated negatively with the tree influence indices. The highest covers of Vaccinium myrtillus, V. vitis-idaea and Hylocomium splendens were observed on patches with thick snow cover. Linnaea borealis, in contrast, was absent from these patches. Pleurozium schreberi and Dicranum polysetum were most abundant on patches with moderate snow. Conclusions: Trees do not only affect ground vegetation through competition, but also have indirect effects associated with uneven snow cover. Our results suggest that, like arctic and alpine species, boreal forest understorey species show differences in their snow affinity.