The hydrocracking behavior of a C-4-C-70 mixture of n-paraffins on a platinum/amorphous silica-alumina catalyst has been analyzed. The influence on the system behavior of operating conditions, i.e. pressure, temperature, H-2/feed ratio and stream velocity, has been investigated by means of experimental data from a bench scale reactor, the last aim being the derivation of a proper model for the reaction system. Because of the high number of species involved, a model which takes into account pseudocomponents (lumped model) corresponding to the cuts of interest for the refinery has been considered. The obtained results show good agreement with experimental data. (C) 2004 Elsevier Ltd. All rights reserved.