Substrate specialization of species in epixyiic communities was studied in old-growth blueberry spruce forests of middle taiga in Kivach Nature Reserve in 2015-2016. The substrate specialization of the species and the systematic groups was analyzed with normalized index of specialization based on occurrence. Tree species, age of dieback, level of decomposition of timber, diameter and height of dead trunks above surface, amount of litter on trunk, bark coverage, moisture content and pH of bark were considered the factors affecting occurrence of species in the epixyiic communities. Epixyiic species in different groups of plants (lichens, liverworts, mosses and vascular plants) were sensitive to different factors. Tree species of deadwood was the most important factor of composition of the epixyiic community for all groups but vascular plants. Other factors by decreasing significance were as follows: amount of litter, degree of decomposition of timber and pH of bark. Substrate specialization differed between lichens and plants. Microsites having high number of species had lower specialization. The highest number of plant species were found on dead spruce, and the lowest was found on dead pines. On the other hand, pines had the highest diversity of lichen species. Substrate attribution of indicator species of old-growth forests was analyzed. Most of the rare and protected species were found on dead coniferous species and aspen. Bark, Coarse woody debris, Decomposition, Indicator species, Lichens, Liverworts, Mosses, Vascular plants