Pt-based catalysts were prepared by ionic exchange over three zeolites with different pore sizes, HMFI, HMOR and HFAU. With them, the effect of zeolite pore size over the transformation of sulfur containing compounds with different molecular dimensions, such as: thiophene (T), benzothiophene (BT) and dibenzothiophene (DBT) was analyzed. For the Pt-containing catalysts, reaction data reveal changes in the overall conversion of T, BT and DBT with zeolite pore size (Pt/HMFI < Pt/HMOR < Pt/HFAU). Hydrogenated sulfur compounds such as tetrahydrothiophene (THT), dihydrobenzothiophene (DHBT) were detected in high yields, being Pt/HMOR the more active catalyst, indicating that hydrogenation took place on some metallic Pt clusters that remained un-poisoned by the sulfur molecule. Moreover, the yields of THT, DHBT and tetrahydrodibenzothiophene (THDBT) remain stable with time on stream, indicating that poisoning by H2S and/or the sulfur compound was not enough to inhibit completely the hydrogenating function of the metal and that at least a fraction of Pt-0 was protected by the zeolite from sulfur poisoning. (C) 2007 Elsevier B.V. All rights reserved.