A Monte Carlo simulation method is used to investigate effects of surface heterogeneity on layering transitions occurring in multilayer films. In particular, we consider systems with randomly distributed quenched impurities and study effects of their concentration and distribution on layering transitions for systems with different strengths of admolecule-substrate interaction. It is demonstrated that in some cases even very low concentrations of impurities can produce qualitative changes in the film behavior. Some of the layering transitions present in homogeneous systems may be destroyed and new transitions may appear.