The relationship between climate change and floods frequency is of great interest for addressing the complex analysis on the hydrologic cycle evolution. In this context, this study aims to assess, by a preliminary investigation, the climate change effects on the floods frequency in several basins of the upper Tiber River, whose area is ranging from 100 to 300 km2. For that, a continuous hydrological model coupled with a stochastic generation of rainfall and temperature has been used. Therefore, a long synthetic series of discharge were generated from which the annual maximum discharges were extracted and, hence, the flood frequency curves were defined. For the stochastic generation of precipitation, the Neyman-Scott Rectangular Pulse model was used, while for the synthetic generation of temperature, an ARIMA model with fractional differentiation was applied. The time series of discharge was assessed by applying a continuous hydrological model developed ad hoc for the investigated basins. The model structure was inferred by investigating the effects of antecedent wetness conditions on the outlet response of several experimental basins located in Central Italy. The analysis proposed here compares the actual time series of precipitation and temperature and the perturbed ones by assuming two different future scenarios obtained by the Global Circulation Model HadCM3. Results showed that geo-morphological and land-use characteristics of basins might have a paramount role in the changing of floods frequency.