No abstracts are to be cited without prior reference to the author.Habitats and benthic–demersal communities in mud volcanoes (MVs) within Spanish waters of the Gulf of Cadiz are being studied in the interdisciplinary LIFE+ project INDEMARES/CHICA to assess their importance for future conservation. Mud volcanoes display morphological and sedimentary complexities that allow different habitat types and communities and have been poorly studied. Sampling was carried out at the summit, on the slopes, depression, and adjacent bottoms of Albolote, Gazul, Tarsis, Pipoca, Anastasya, and Chica MVs (340–760 m depth). Otter trawls (12 samples), beam trawls (27), and boxcorers (30) were used to characterize the spatial distribution of habitats and communities. More than 500 species have been found to date, including new records for this area. In Gazul and Chica MVs, sponge aggregations (Asconema setubalense, Petrosia sp., Phakellia sp.) and coral gardens (Acanthogorgia spp., Callogorgia verticillata, Madrepora oculata) occur. Sea pen and burrowing megafauna communities (Funiculina quadrangularis, Kophobelemnon stelliferum, Pennatula cf aculeata) with bamboo corals (Isidella elongata) were found in Tarsis, Pipoca, and Anastasya MVs. Benthic communities associated with leaking gases (Habitat 1180 Natura 2000 network) were found on the summit of Anastasya, dominated by frenulate polychaetes (Siboglinum sp.) and the bivalves Acharax sp. and Lucinoma sp. This represents the first record for this type of habitat and community within Spanish waters. Differences between MVs and their associated habitats and communities may be linked to substrate types (mud breccia vs. hard bottoms with authigenic carbonates), seepage activity (active vs. latent conditions), and the MOW influence, increasing the biodiversity and spatial hetereogenety within the Gulf of Cadiz.