The main goal of the research was to study differences in groundwater runoff parameters development under different geological conditions, with the emphasis to extreme climatic conditions in dry years. Groundwater runoff parameters, represented by values of the base flow, groundwater recharge and groundwater storage were modelled using the BILAN model, which is a lumped parameter hydrological model. Three sub-catchments were selected – the Upper Nitra, Upper Poprad and Upper Top a in the Western Carpathians. The catchments differ not only by geological, but also by climatic conditions. The results showed that the lowest groundwater runoff represented by the specific groundwater runoff values forms in the crystalline rocks of the Vysoké Tatry Mts. The highest values were obtained in the Upper Nitra River sub-catchment. Results obtained by hydrological model were compared with values of groundwater runoff calculated using the method of Kille and the BFI+2 model. Different years were identified in evaluated catchments as the dry years. While in the Upper Nitra River sub-catchment, years 1983 and 1989 were identified as dry years, in the Poprad and Top a River sub-catchments, the driest years were 1986 (in both catchments) and 1982 (Top a) and 1993 (Poprad). The highest decrease of the groundwater runoff in the driest year reached 30 % in the Upper Nitra, 41 % in the Upper Top a and 19 % in the Upper Poprad Rivers sub-catchments.