Self-purification is a frequent phenomenon for Suceava River in the homonymous city. Self-purification is documented for N - NH4+, N-2(-), NO2-, N - NO3-, Total Nitrogen (TN), Total Phosphorus (TP) and SO42-. During the 2006-2011 time interval, the monthly average self-purification percentages were: 18.7% N - NH4+, 36.3% N - NO2-, 14.4% N - NO3-, 12% TN, 35.4% TR 11.96% SO42- (2 sampling points: upstream and downstream the city). The main factors that contribute to the observed self-purification are: the iron-rich streamwater, the sedimentary and biological retention, the co-treatment of different contaminated waters and the hydraulic jumps. There are seasonal variations in average and maximum monthly self-purification percentages. When the water pollution is higher, the self-purification process is stronger.