The article deals with the least-studied taxonomic group of mammals in the Green Belt of Fennoscandia (GBF) and Karelia as a whole – bats (Chiroptera, Vespertilionidae). The aim was to determine the status of species in the process of their inventory us-ing traditional and modern research methods. For the first time, an integrated assess-ment of the species composition, relative abundance (%) and relative numbers (ind./km of the route) of bats during the hibernation period and summer activity is given for GBF. Underground hibernacula (mines and former military concrete bunkers) were mon-itored in 2009–2018 years. Up to 25 bats of 5 species overwinter in the largest hibernac-ulum described for Karelia (Ruskeala) – the northern bat Eptesicus nilssonii Keyserling, Blasius, 1839, Brandt’s bat Myotis brandtii Eversmann, 1845, whiskered bat M. mystac-inus Kuhl, 1817, Daubenton’s bat M. daubentonii Kuhl, 1817, and brown long-eared bat Plecotus auritusLinnaeus, 1758. The northern bat dominated, with a relative abundance of 65.8 %. The history of bats hibernating in the Ruskeala Mining Park in connection with the reconstruction of the gallery was traced. Changes in the habitat conditions for bats and their consequences for the diversity, species numbers and hibernation ecology are shown. In summer, in addition to the species recorded at hibernacula, car transect and control point surveys using the Song Meter SM2 Bat+ (USA) static ultrasound detec-tor and Kaleidoscope Pro software (ver. 3.1.1) detected common noctule Nyctalus noct-ula Schreber, 1774, parti-coloured bat Vespertilio murinusLinnaeus, 1758, Natterer’s bat M. nattereri Kuhl, 1817, and pond bat M. Dasycneme Boie, 1825. The summer censuses reached up to 66°23ʹN, and the northern bat also dominated the records, with 52.4 % rel-ative abundance, and 0.238 ind./km route relative numbers. The high prevalence of bats at waterbodies in GBF (69.2 %) and its species-specific features at waterbodies of var-ious categories are shown. The first inventory of bats in protected areas within GBF has significantly expanded the list of bat species known in these territories. In general, studies have shown the northern bat predominated in the bat communities both at hibernacula and during the summer period. The northernmost records of species, including migrants, have been updated, modifying the previous ideas about their distribution in the region.