Coralligenous assemblages are some of the most important Mediterranean biotic communities from an ecological, economical and aesthetic standpoint, although the data about them in the Adriatic is lacking. The specific goals of this thesis were to determine the composition and structure of sessile macrobenthos, and spatial variability for the Northern Adriatic coralligenous communities based on the composition and abundance of taxa and main ecological groups. 72 taxa were determined by photographic sampling, 82% of which were present at all of the investigated sites. Sponges had the greatest species richness (28). Based on the surface area covered, the main contributors were algal bioconstructors - red calcareous encrusting algae, followed by green turf-forming algae and sponges. The most abundant species were Rhodophyta of genus Peyssonnelia. Anthozoans and Bryozoans were the most abundant animal bioconstructors. Gastrochaena dubia was the most represented bioeroder. The morphological composition indicates a low structural complexity with approximately 70% of the surface area covered by a basal layer, while the upper layer was poorly developed. Multivariate biodiversity patterns based on the composition and abundance of taxa and ecological groups differed between sites, confirming a significant spatial variability of the coralligenous assemblages. The qualitative and quantitative data documented in this paper could serve as a starting reference for the investigated coralligenous communities enabling their future assessments within NATURA 2000 sites.