The species composition and abundance of macrozoobenthos was studied in rapids and backwaters of the Kem’ River (draining to the White Sea). 93 species and supra-species taxa of invertebrates were identified. Zoobenthos of the rapids was more diverse, the bulk of it made up of amphibiotic insects at the larval stage – mayflies of the family Baetidae (Ephemeroptera), caddisflies of the families Hydropsychidae and Rhyacophilidae, stoneflies (Plecoptera), dipterans of the subfamily Orthocladiinae. The backwaters are poorer in species diversity, the species of chironomids of the subfamily Chironominii predominate. The zoobenthos biomass in the rapids (1112–2150 ind./m2 and 1.7–6.9 g/m2) is mainly composed of Trichoptera, Plecoptera and Bivalvia. The backwaters are poor in zoobenthos (390–1210 ind./m2 and 0.8–2.8 g/m2). The biomass is formed by Bivalvia and Gastropoda, Oligochaeta and Chironomidae. Local, highbiomass (up to 460 g/m2) aggregations of large bivalves Anodonta cygnea have been found. In the trophic structure, the most indicative is the share of passive filter feeders, which is high in the rapids in the lower reaches of the river and downstream of flowage lakes. According to the composition of saprobity indicator organisms, watercourses of the Kem’ River catchment belong to the β-mesosaprobic zone.