This work investigated the decomposition of dilute N2O from gas streams with various oxygen contents by using a plasma-catalytic process over metal oxide catalysts supported on gamma-Al2O3. Among the metals explored (Ru, Co, Cu, V, etc.), Ru was found to be the best catalyst for the decomposition of N2O in a plasma-catalytic reactor, and most of the experiments were conducted with alumina-supported Ru. The effects of applied voltage, reaction temperature, O-2 content, gas flow rate and initial N2O content on the decomposition efficiency and byproducts formation were examined. Compared to the catalyst-alone case, the presence of plasma enhanced the decomposition efficiency by 30-50%, depending on the operating condition. The increase in the oxygen content from 0 to 20% largely decreased the catalytic decomposition efficiency, whereas in the presence of plasma N2O could be successfully decomposed even at 20% O-2 content. The decomposition efficiency was not a strong function of the initial N2O concentration in the range of 225-1800 ppm, exhibiting pseudo first-order reaction kinetics. Without O-2, there were negligible byproducts, but in the presence of O-2, NO and NO2 were formed mainly due to the plasma-induced reactions between background molecules such as N-2 and O-2. The results obtained in this work showed the feasibility of plasma-catalytic process for the abatement of N2O.