In order to develop constructed wetlands for treating hydroponic wastewater in greenhouses, removal efficiencies and decomposition velocities of pollutants in constructed wetland were investigated for treating hydroponic wastewater. Removal rates of BOD, COD, SS, T-N and T-P in effluent in constructed wetlands were 88%, 79%, 92%, 64% and 92%, respectively. The decomposition velocities (K; day<sup>-1</sup>) of pollutants in 1st HF bed of constructed wetlands were higher in the order of SS (0.54 day<sup>-1</sup>) > BOD (0.39 day<sup>-1</sup>) > COD (0.27 day<sup>-1</sup>) > T-P (0.26 day<sup>-1</sup>) > T-N (0.06 day<sup>-1</sup>). In 1<sup>st</sup> HF bed of constructed wetlands, the decomposition velocity of SS was rapid than that for BOD, COD, T-N and T-P in constructed wetland for treating hydroponic wastewater. The decomposition velocity (K; day<sup>-1</sup>) of pollutants in 2<sup>nd</sup> HF bed of constructed wetland were higher in the order of T-P (0.52 day<sup>-1</sup>) > BOD (0.28 day<sup>-1</sup>) > COD (0.15 day<sup>-1</sup>) > T-N (0.06 day<sup>-1</sup>) > SS (0.10 day<sup>-1</sup>). In 2<sup>nd</sup> HF bed of constructed wetlands, the decomposition velocity of T-P was rapid than that for BOD, COD, SS and T-N in constructed wetland for treating hydroponic wastewater.