This study compares species composition, local species richness, beta diversity and species pool of beech-dominated forests in three main mountain systems in central Europe. We used a recently compiled representative data set of 5946 vegetation plots recorded in the Eastern Alps, Bohemian Massif and Western Carpathians. Effects of bedrock type, region, altitude and spatial variables represented by PCNM (principal coordinates of neighbour matrices) axes were analyzed. All the predictor variables studied had highly significant effects on species composition. Effect of altitude was largely independent of effects of bedrock and regions, which shared the majority of explained variation in species composition. Spatial (PCNM) variables together accounted for the largest part of the variation in species composition. Communities on carbonate bedrock were differentiated by numerous calcicolous species. Within the group of silicate bedrock types, beech forests on volcanic rocks were differentiated by occurrence of a set of eutrophic and nitrophilous species. The Alps and the Carpathians were similar in species pool size, beta diversity and increasing species richness with altitude, which is related to extensive areas of carbonate bedrock at high altitudes in these mountain systems. The highest local species richness occurred at high altitudes in the Alps. Beech forests in the Alps were floristically well differentiated from the other regions by a group of species restricted to this region, which is probably a consequence of the postglacial migration history. Limited species richness and species pool were found to be typical of the Bohemian Massif; they seem to be partly linked to predominance of siliceous bedrock in this region and partly to the greater distance to beech-forest glacial refugia.