The article presents the results of a study of the lichen flora in a Petrozavodsk city’s green space dominated by spruce forests of the true-moss group, which have a typical mid-boreal appearance. The consequences of long-term recreation are seen in all communities. Field surveys were carried out by selecting 30 sample plots (25×25 m) in 11 forest types, where the total lichen species richness was studied on all types of substrates. A total of 157 species were found, which accounts for 38 % of the species diversity of lichens in Petrozavodsk including historical data, and 50 % of the current diversity. Crustose lichens predominate in the study area (71 %), fruticose and foliose species contribute 16 and 13 %, respectively. In terms of substrate affiliations, most of the species (74 %) belong to the epiphytic group; epixylic, epigeous and epibryophytic lichens have 18, 7 and 1 %, respectively. In the lichen flora, 2 species (Bacidina chloroticula and Scoliciosporum pruinosum) are new for the territory of the Republic of Karelia, 24 for the Petrozavodsk city, and 29 for the Karelia olonetsensis biogeographic province of Eastern Fennoscandia, to which most of the city territory belongs, including the study area. Three species (Arthonia vinosa, Chaenotheca stemonea, and Psilolechia clavulifera) are listed in the Red Data Book of the Republic of Karelia, and three species (Calicium denigratum, Chaenotheca brachypoda, and Steinia geophana) are included in the list of flora and fauna species requiring special attention to their natural environment and recommended for biosurveillance. Five of the lichen species encountered are indicators of biologically valuable forests. The results indicate a high biological value of the studied area.