UV irradiation of the Pb2+/ZSM-5 catalyst prepared by an ion-exchange method in the presence of N2O leads to the decomposition of N2O into N-2. This reaction is found to be dramatically enhanced by the addition of propane to produce N-2 and oxygen-containing compounds such as ethanol or acetone. UV light effective for the reaction lies in wavelength regions shorter than 250 nm where the absorption band of the Pb2+ ion ([Xe] 4f(14)5d(10)6s(2) --> [Xe] 4f(14)5d(10)6s(1)6p(1)) exists, indicating that the excited state of the isolated Pb2+ ions plays a significant role in this decomposition of N2O both in the absence and the presence of propane, and the role of propane is found to be a capture of oxygen atoms formed by the decomposition of N2O.