The spatial distribution of the polychaete fauna in the subtidal soft-bottoms of the Ensenada de Baiona (Galicia, NW Spain) was studied by means of quantitative sampling and multivariate analyses. Several faunistic assemblages were determined, which were closely related to the sediment distribution pattern in the inlet. The coarse-medium sand fauna was mainly dominated by syllids and pisionids. Finer sediments (fine sand to mud) showed a greater abundance of deposit-feeding species, mostly spionids, cirratulids and capitellids. The greatest number of species and diversity were found in mixed sediments with medium and fine sand. Organically enriched muds around Baiona harbour have an impoverished fauna, with a high dominance of Cossura pygodactylata Jones, 1956.