Polyhumic dystrophic rivers are very rare in Poland and polyhumic rivers (both poly- and dystrophic) are weakly researched in general. The aim of the study was to present a detailed faunistic and ecological analysis of the water mites of polyhumic dystrophic rivers from Janów Forests Landscape Park (central-eastern Poland) and to compare the Hydrachnidia communities of those rivers with the Hydrachnidia of non-polyhumic rivers of this area. In small, fully polyhumic rivers Hydrachnidia fauna was poor in species and individuals, the populations of most species were very small and the characteristic feature of these rivers was very low species diversity. Therefore, the pronounced dystrophy of small polyhumic rivers should be considered a factor restricting the development of larger Hydrachnidia populations. In partially polyhumic rivers the water mite fauna was more diverse than in fully polyhumic rivers. The greater diversity of fauna resulted from the migration of species and individuals from the upper reaches of the river (non-polyhumic) and from greater habitat diversity. As a general conclusion we can say that in the fauna of polyhumic dystrophic rivers it is impossible to indicate species that could be considered characteristic of these habitats and that distinguish the Hydrachnidia communities of polyhumic rivers from those of non-polyhumic rivers. The Hydrachnidia communities of polyhumic rivers differ from those of non-polyhumic rivers in terms of population size. Quantitative impoverishment of fauna is observed in polyhumic rivers (especially small, fully polyhumic ones). More research should be done to determine specificity of water mite fauna of polyhumic rivers.