Caddisflies (Trichoptera) are significant group of macrozoobenthos and belong, to the most important bioindicators of water quality. In this thesis, we studied caddisfly communities in selected locations of running waters in eastern Slovakia. Samples were collected at 31 localities. We recorded 35 caddisfly taxa. The most frequently occuring taxa were species from the family Hydropsychidae and Limnephilidae. The statistically significant relationship of taxonomic diversity has been confirmed with factors pH, phosphorus concentrations, conductivity and altitude. Signifficant relationship confirmed with these factors means that the anthropic impact on watercourses can be one of the major factors with negative impact on the diversity of Trichoptera taxa.