Based on a model proposed by Olsson et al. (Surf. Sci. 2003, 529, 338), a study is made through a mean field scheme of the effect of steps-terraces superficial heterogeneity, whose energy differences have been determined recently by means of density functional theory (DFT), in the catalytic reduction reaction of NO by CO over palladium. Several aspects are seen, such as the relation between the activities produced in both sectors of the surface as a function of temperature and the energy difference between them, the activity and coverage versus the temperature and the gas phase concentration curves, and the effect on these variables of the activation energy values on the steps of some stages of the kinetic mechanism. The system shows a reaction order with respect to CO and NO that changes sign between low and high temperatures, from negative to positive in the case of CO and the opposite for NO.