A Monte Carlo simulation study is made of the sensitivity of the CO oxidation reaction to changes in the characteristics of the catalyst's surface on which the type of oxygen adsorption mechanism is dependent. Infinite rate models of the Ziff, Gulari, and Barshad (ZGB) type, and mechanisms having kinetics parameters of actual experiments from the literature are studied. It is shown that, if linear adsorption is assumed, the structural insensitivity becomes apparent in the phase diagram but not in the production of CO2. In the case of structural sensitivity it is seen that surface heterogeneity leads to a change in the character of the phase transition curve, and also allows information about the surface to be obtained from the shape of the transition curve.