The establishment of native woodland in the moorland areas of upland Britain is increasing. However, there is no clear basis on which to predict either the effect of this on the ecology of the mountain hare, or the effect of mountain hare on woodland establishment. This study investigates the feeding ecology of the mountain hare, a primarily moorland inhabitant in upland Britain, in an upland landscape containing a newly established native woodland and also the potential impact that they may have on regeneration of native woodland species (Pinus sylvestris, Betula pubescens and B. pendula). The mean home range size, determined by radio-tracking, of male mountain hares was 12.1 ha and females 8.9 ha. The native woodland habitat was not preferentially selected by mountain hares in summer or winter. Faecal n-alkane and long-chain fatty alcohol analysis revealed that P. sylvestris and B. pubescens were minor components of the diet in all seasons. The diet of both male and female hares was dominated by Calluna vulgaris in winter and by grasses, sedges and rushes in summer. Annual measurements of browsing by mountain hares on P. sylvestris and B. pendula saplings at eight sites throughout Scotland, showed that on average only 5.8 % of trees sustained browsing each year. Relative hare abundance, tree density, tree species and ground vegetation height did not predict the extent of browsing damage by mountain hares. In contrast, a field-based planting experiment involving nursery grown B. pubescens saplings, had higher local hare densities and revealed that mountain hares do browse saplings extensively and that season, tree density and ground vegetation height are important in determining the extent of browsing. Seasonal habitat utilisation of the experimental plots by mountain hares fluctuated in relation to the frequency of browsing. In general, the results showed that moderate densities of mountain hares are unlikely to inhibit regeneration of native woodlands However, the likelihood of damage will increase if trees occur at high densities and if local hare density is high.