Presented diploma thesis is dealing with the determination of T-years maximal discharges in small watersheds for the purpose of flood protection. We have chosen three experimental watersheds, which have similar characteristics of natural conditions. In the Poľana mountain range are located watersheds of watercourses Hučava (watershed area S_p 41,37 km^2; forestation ℓ 80,83 %; average watershed slope 〖ΦI〗_pov 28 %), Hutná (S_p 38,99 km^2; ℓ 61,51 %; 〖ΦI〗_pov 26,2 %) and Kamenistý potok (S_p 48,86 km^2; ℓ 80,21 %; 〖ΦI〗_pov 16,8 %). We have compared values of N-years maximal discharges determined by Slovak Hydrometeorology Institute (SHI) and determined values according to academician Dub. Calculated values by the CN-curve method has been compared with the simplified calculation by hydrological modeling system (HEC-HMS), software which has been created for simulation of hydrological processes in watersheds. Simulation of T-years maximum discharge has been created for different rain durations (30, 60, 90, 120, 300 and 450 min) and different rain intensities (50, 75, 100, 125 mm). Next part of this work deals with a theoretical scenario simulation of land use change, where the forest has been replaced by grassland. This change of land use represents a simulation of land use change, which may occur with a potential change of forest management, unexpected disaster or future climate change. Last part of this work deals with question after other authors, if relatively greater value Q_100= 70 (m^3 s^(-1)) estimated by SHI, for Hutná watercourse, if it is the actual value of 100 –year discharge. Method, which is in our opinion suitable for determination of T-years maximal discharges in small watersheds in the conditions of Slovakia, has been chosen.