Summary information about water balance of Carpathian temperate forest ecosystems is presented in the paper. The main role in the forest water balance plays evapotranspiration that determines the runoff water amount. Evapotranspiration from forest ecosystems includes (example of middle mountain region - 850 m a. s. l.): transpiration (30 - 35 %), interception (18 - 29 %), and evaporation (7 - 8 %). Analysis of precipitation-runoff processes in relation to forests has shown that forests may play a crucial role in a runoff regime especially in maximum runoff course. From the above mentioned reasons it is necessary to take into account the active function of water management of forest ecosystems in the landscape and forest management mainly in the flood sensitive catchments.