A 19-year old combined pond-wetland system in Sweden effectively removes pollutants from stormwater runoff. The system reduced flow by 60-76% and removed high percentages of TSS, TP, Cd, Cu, Pb, and Zn. It also showed variable removal of Ni, TN, NH4-N, and NO3 + NO2-N. The wetland enhanced treatment performance and peak flow reduction compared to the pond alone. Factors like dry days, seasons, temperature, and rainfall influenced pollutant removal efficiency. This study highlights the efficiency of older pond-wetland systems in treating stormwater runoff.