trophic structure of benthic communities is influenced by the availability of food resources which indeed may be conditioned by stream size, shading and substrate. this study aims to analyze the distribution of macroinvertebrate functional feeding groups in different habitats of mountain streams (córdoba, argentina) and to assess the environmental variables conditioning this distribution at the habitat level. four streams were sampled in two hydrological periods (high and low discharge) and three benthic samples were taken in riffles and runs of coarse and fine substrate. gathering collectors were dominant in most of the habitats, streams and periods except in riffles during the low water period in which filtering collectors dominated. at the habitat level, current velocity, substrate, abundance of macroalgae and twigs and leaves were the most important variables explaining functional feeding group distribution. functional feeding group abundances varied in relation to the stream, the hydrological period and the habitat. the dominance of collectors demonstrates the importance of the role of this functional group and that fine detritus is the main food resource in these lotic ecosystems. the phenology and life history of the species, and the amount and type of organic matter retained in each habitat may explain the observed spatial-temporal patterns.