The zooplankton composition, abundance and biomass of six small water reservoirs were studied in autumn months in 2008. The reservoirs are localised on the both sides of the Malé Karpaty Mts and differ in respect to the land use and atrophic pressure. The highest species diversity of planktonic crustaceans (34 cladocerans and 11 copepods), the low abundance and biomass of zooplankton was found in reservoir situated in the Záhorská nížina lowland. As for water quality, based on zooplankton structure, chemical parameters and phytoplankton concentration are the better betamesosaprobic and oligosaprobic degree. From the aspect of cladocerans diversity, these reservoirs were rich and should be protected. On the other hand, high trophy, high abundance and biomass of zooplankton, mainly rotifers and Bosmina longirostris , documented the fish predation in reservoir situated in the Podunajská nížina lowland.