The aim of the present study was to examine how the vegetation structure of the forest, shrub and field and ground layer affect the habitat use of mountain haresLepus timidus Linnaeus, 1759 in summer (May–September) in southern Finland. The structure of each vegetation layer in woodlots throughout the entire study area of 20 km2 was measured. We analysed the vegetation data using principal component analyses (PCA) that arranged the woodlots along a gradient within each vegetation layer. Data on habitat use was gathered between 1998 and 2000 from 11 radio-collared mountain hares. The core areas of the home ranges of hares were determined and the vegetation structure of these areas was compared with the mean of the entire study area (core area, periphery area and control area). A similar shrub layer gradient was identified by PCA for seven out of the 11 hares. Hares preferred thickets of willowSalix spp., downy birchBetula pubescens, and sprucePicea abies. The hares did not show a consistent preference for the forest and ground levels. The results suggest that dense understories are important in the mountain hare’s habitat use, probably because they offer both food and shelter.