In the Weddell Sea cumaceans are well diversified with 29 species or subspecies caught during the EPOS 3 cruise. Nine of these are new species or subspecies: Diastylis anderssoni armata, D. enigmatica and D. galeronae, Leucon polarsterni and L. weddelli, Atlantocuma elongatum (type of the new subgenus Antarctocuma), Campylaspis breviramis, C. excavata and C. quadridentata. One Eudorella remains unidentified. Diastylis alvesae nom. nov. is proposed for Diastylis hirsuta Petrescu and Bacescu, 1990 homonym of D. hirsuta Lomakina, 1955 but which is not the same species. Qualitatively, between 200 and 2000 m there are three patterns of species distribution: species with a large depth range (200 to 1000–2000 m), deep-water species which inhabit deposits around 500 m, and species living from 200 to 500–600 m. The presence of an ice shelf does not permit investigation of littoral bottoms (0–200 m) in this area. Quantitatively, in the Weddell Sea cumaceans are abundant. Multibox-corer samples indicate a population density of 74 individuals m-2 between 200 and 1200 m