The pumpkinseed sunfish Lepomis gibbosus introduced into Lake Banyoles (Spain) were predominantly littoral but there was a tendency of large fish to use deeper zones. Their diet was dominated by littoral macrobenthos, particularly amphipods (Echinogammarus sp.). There was ontogenetic variation in the diet, with small young-of-the-year (LF<4 cm) feeding on several littoral microcrustaceans, especially the cladoceran Ceriodaphnia reticulata, whereas larger fish shifted to a freshwater shrimp (Atyaephyra desmaresti), snails and damselfly larvae. Seasonal variation in diet was linked to resource availability, with consumption of fish eggs and plant debris in spring and summer. In autumn, pumpkinseeds were partially zooplanktivores, preying on the cladoceran Daphnia longispina. The diet of pumpkinseeds in Lake Banyoles and other Iberian populations shows less molluscivory than North American populations. The potential ecological impact of this successful exotic species involves mainly predation on fish eggs and molluscs.