Kinetics of model catalytic processes proceeding on inhomogeneous surfaces is studied. We employ an extended mean-field model that takes into account surface in homogeneities. The influence of surface diffusion of adsorbent on the kinetics of the catalytic process is investigated. It is shown that diffusion is responsible for differences in the reaction rate of systems with different arrangements of active sites. The presence of cooperative effects between inactive and active sites is demonstrated and the conditions when these effects are important are discussed. We show that basic catalytic phenomena on nonuniform surfaces can be studied with mean-field modeling methods. (C) 2007 Elsevier B.V. All rights reserved.