The aim of this study was to investigate, by use of d13C and d15N, the diet of co-occurring intertidal molluscs species within a community dominated by the oyster Crassostrea gigas and its epibiont, the common Atlantic slipper limpet Crepidula fornicata. The results showed that the d13C versus d15N values of C. gigas differed from those of the deposit feeders considered but also from the other suspension-feeding molluscs (i.e. Mytilus edulis, Cerastoderma edule and C. fornicata), being more depleted in 13C and in 15N. The results suggest more similarities in the assimilated food sources of C. fornicata, C. edule and M. edulis. In particular, the d13C and d15N differences between C. gigas and C. fornicata suggest that these associated suspension feeders in many shellfish culture areas may not necessarily be competitors for food sources when food is not limited. [KEYWORDS: Benthic food web · d13C · d15N · Molluscs · Crassostrea gigas · Crepidula fornicata · Oosterschelde] ; The aim of this study was to investigate, by use of d13C and d15N, the diet of co-occurring intertidal molluscs species within a community dominated by the oyster Crassostrea gigas and its epibiont, the common Atlantic slipper limpet Crepidula fornicata. The results showed that the d13C versus d15N values of C. gigas differed from those of the deposit feeders considered but also from the other suspension-feeding molluscs (i.e. Mytilus edulis, Cerastoderma edule and C. fornicata), being more depleted in 13C and in 15N. The results suggest more similarities in the assimilated food sources of C. fornicata, C. edule and M. edulis. In particular, the d13C and d15N differences between C. gigas and C. fornicata suggest that these associated suspension feeders in many shellfish culture areas may not necessarily be competitors for food sources when food is not limited. [KEYWORDS: Benthic food web · d13C · d15N · Molluscs · Crassostrea gigas · Crepidula fornicata · Oosterschelde]