The distribution patterns of the common arctic zooplankton species Oithona similis and Oithona atlantica were investigated in the Barents Sea during warm and temperate years. The maximum abundance and biomass of Oithona spp. (159 x 10(3) ind./m2 and 38.8 mgC/m2, respectively) were recorded in the waters of Atlantic origin. O. atlantica occurred in Arctic waters only during anomalously warm years. It has been found that the quantitative characteristics of O. similis were negatively correlated with salinity and the winter NAO index, whereas the abundance of O. atlantica in Atlantic waters was positively correlated with the temperature anomaly. It is found that the abundance and biomass of Oithona pp. were comparable with the values recorded in other Arctic regions.