The bryophyte flora and its environmental correlates were studied on 28 treeless cliffs and 18 treeless talus slopes in forested river valleys of the southern Czech Republic. The diversity of bryophyte assemblages was assessed through species richness and spectra of distribution-range types, growth forms and life strategies, using analysis of covariance. Species richness of cliffs increased with their area but this was not the case for talus slopes, where a high microtopographic heterogeneity appeared to be the key factor governing diversity. No habitat island effects were detected for cliffs; there were no differences between isolated cliffs and cliffs found in the neighbourhood of other cliffs or talus slopes. Island effects were not studied for talus slopes as they were nearly always found in clusters with cliffs and other talus slopes. Talus slopes were characterized by a strong effect of the ecotone between forest and open talus, with ecotonal vegetation being more diverse than the central part of talus slopes. However, no ecotone effect was found on cliffs. The effect of potential irradiation, used as a proxy for moisture availability, was weak on cliffs but strong on talus slopes where more insolated slopes had lower diversity, more temperate and fewer boreal species, a predominance of short turf or cushion-like mosses over large bryophytes and a higher proportion of the colonist strategy, as opposed to perennial stayers and long-lived shuttle species. On cliffs, base-rich rocks had higher total species richness but a lower proportion of hepatics, fewer suboceanic and more submediterranean species, and more small turf or cushion-like mosses. The effect of base status was not assessed for talus slopes as they were all formed from acidic rocks. These results demonstrate that cliffs and talus slopes in the same area are quite different habitats and each is characterized by distinctive environmental conditions.