The use of methods dealt with in computational chemistry for the design of efficient catalysts has become increasingly frequent. In our study, molecular modeling methods were used to find the catalytic sites of a Pt-Sn/gamma-Al2O3 catalyst. Five different catalyst models including one support model were constructed. With the docking method, the most probable locations of hydrocarbon molecules on the micropore surface were determined. The host-guest interaction energy was calculated for all locations, using the CVFF approach. The results revealed a very strong influence of the platinum centers and a considerably weaker one of the tin centers, comparable to those of the support atoms. Calculations were also carried out to establish the distance of the adsorbed hydrocarbon molecules from the catalyst model-the distance of the shortest contact. Aliphatic hydrocarbons adsorb much closer to the micropore surface than do cyclic hydrocarbons. (C) 2004 Elsevier B.V. All rights reserved.