ABSTRACT: Siphonostomatoid copepods are often numerically important at deep-sea hydrothermal vents but their role in vent food webs has been little investigated. We examined food sources of 2 vent copepod species, Stygiopontius quadrispinosus and Benthoxinus spiculifer, and their potential role in the diet of paralvinellid worms, using a combination of complementary techniques: (1) stable carbon and nitrogen isotopes, (2) fatty acid composition and (3) morphological examination of copepod mouth structures using scanning electron microscopy. All 3 techniques revealed distinct differences between the 2 copepod species. Fatty acid composition identified bacteria as the main food source for both copepod species and indicated that S. quadrispinosus may be more specialised than B. spiculifer. Stable carbon and nitrogen isotopes provided further evidence that the 2 species partition food sources but feed at the same trophic level. The fatty acid composition and stable isotopes of both paralvinellid worms showed that they are generalists, with a varied diet. Further, in samples where S. quadrispinosus were highly abundant, both worms had stable carbon and nitrogen isotopic compositions that indicated that they were feeding on copepods. Although neither worm appeared anatomically equipped for seizing live copepod prey, we suggest that dead copepods may be consumed along with other particulate debris by the paralvinellid worms. The contribution of copepod remains to the detrital pool in these mineral substratum habitats remains to be quantified.