The study evaluated seasonality of median monthly discharge in selected carpathian rivers of the upper Vistula basin, namely the Kamienica Nawojowska – Łabowa profile, the Rudawa – Balice profile, and the San – Przemyśl profile. To this end, Colwell’s indices, analysis of autocorrelation and spectral analysis were used. The data for calculations, i.e. a series of observations of daily discharge from the multi-annual period of 1983-2012, were obtained from the Institute of Meteorology and Water Management – National Research Institute in Warsaw. The study showed no regular seasonality of median monthly discharge in the analyzed rivers. This was evidenced by the value of Colwell’s indices, with contingency M accounting for less than 50% of predictability P in the hydrological regime of the studied rivers. This conclusion was also confirmed by statistically significant results of the autocorrelation analysis and results obtained from the spectral analysis. The study indicated that Colwell’s indices may be a simple and effective tool for evaluating seasonality of discharge in rivers of the southern Poland.