Habitat structures of stream ecosystems are fundamental drivers in the formation and maintenance of benthic assemblages in running water contexts. In this presentation I will focus on two major structural aspects of stream habitat: (i) canopy cover, which controls light availability for primary producers, and (ii) riffle/pool structures, which determine current patterns and water depths of habitat. Consideration will be given to how these habitat structures may exert influences upon community assemblages in stream ecosystems.