Artículo de publicación ISIUsing Monte Carlo simulation experiments, a study is made of the effect of the superficial coordination number in a square lattice of sites for the monomer–dimer surface reaction (Ziff, Gulari and Barshad model) in the case of disordered substrates showing geometric heterogeneity of the sites, such as the percolation clusters. An analysis is made of the change in character of the phase transitions and in the size of the reactive window in the phase diagram, and the results were also compared with mean field theoretical calculations for disordered systems.