The effects of gas composition on hybrid gas-water gliding arc discharge plasma reactor have been studied. The voltage cycles are characterized by a moderate increase in the tension which is represented by a peak followed by an abrupt decrease and a current peak in the half period (10 ms). Emission spectrum measurements revealed that center dot OH hydroxyl radicals are present in the discharge with feeding any gas. The H(2)O(2) concentrations reach 38.0, 15.0, 10.0, and 8.0 mg/l after 25 min plasma treatment with oxygen, argon, air, and nitrogen, respectively. O(3) was produced when oxygen and air are used, but not when nitrogen and argon. The O(3) concentration reached the highest value 1.0 mg/l after 25 min plasma treatment with oxygen feeding gas, but gradually decreased to 0.2 mg/l after that. With feeding nitrogenous gas, NO(2) (-) and NO(3)(-) byproducts were formed by the plasma chemical process.