The species and size selectivity of longlines using small hooks were studied off the south coast of Portugal using 'Mustad' brand round bent flatted sea hooks (Quality 2316 DT) numbers 15, 13, and 11 baited with razor shell clam (Ensis siliqua).Hook numbers 13 and 11 are 49 and 109% larger than number 15 hooks in terms of overall size (maximum width x maximum length). A total of 39,900 hooks were fished in 45 sets and 35 species of fish and cephalopods were caught. As a group, 13 species of seabreams (Sparidae) dominated the catch by numbers (58%) and weight (73%). Six species of seabreams along with the greater weever fish (Trachinus draco) accounted for 81% of the total catch by weight, with the common or white seabream Diplodus sargus being the most important (29%). Catch size distributions by hook size were in general, highly overlapped for all species, with hook size having little apparent effect on minimum size at capture. All hooks caught a wide range of sizes per species, but the catch rate (number of fish per 100 hooks) was significantly lower for the largest hook. Except for the black seabream Spondyliosoma cantharus, capture of illegal sized or immature fish was minimal. Small increases in average size with hook size were evident for four species: Diplodus sargus, D. vulgaris, Lithognathus mormyrus, and Serranus cabrilla. No differences in size selectivity were detected for Boops boops, D. annularis, Spondyliosoma cantharus and Trachinus draco. A skew-normal model adequately described differences in size selectivity in five of six species.