Many species shift their distribution northwards due to changing climate, which may bring previously isolated species into contact. In some cases, this can lead to competition and crossbreeding among congeneric species. Due to milder winters, several hare species (Lepus spp.) have shifted poleward or to higher elevations and currently occur in sympatry. There are limited data on the spatial ecology of northern brown hares (L. europaeus), and on possible joint space use with mountain hares (L. timidus), although species are known to frequently crossbreed. We estimated home ranges of 12 brown and 12 mountain hares in eastern Finland using GPS telemetry. The total home-range median areas were 111 ha for brown hares and 105 ha for mountain hares. The median core areas of these species were 5 and 3 ha, respectively. Individual home ranges and core areas of the studied species overlapped. Interspecific interaction seems to be frequent during the breeding season, which also enables crossbreeding.