Adsorption equilibria and adsorption rates of dinitrogen oxide, N2O, on hydrogenated synthetic mordenite (HM) are studied using a batch-wise constant volume cell. The amount of N2O adsorbed is determined from the pressure decrease noted by the change in manometer levels of mercury, where N2O initial concentration is as high as 70 kPa. The adsorption of the N2O/HM system follows a Langmuir type isotherm accompanying low heat of adsorption generated by physical adsorption. Adsorption rates of N2O on HM were analyzed based on a surface diffusion model. It is shown that the increases in the amount of N2O adsorbed with increasing time can be well represented by the model using surface diffusion coefficients decreasing with the increases in the amount of N2O adsorbed. A relationship between surface diffusivity and pore size of zeolite is proposed.