The influence of the Rh content of catalysts supported on SiO₂–Al₂O₃ (SIRAL 70 and 80, with 70 and 80 wt% of SiO₂) on the activity and selectivity for selective ring opening of decalin was studied at 325 and 350 °C. An optimum metal content was found at 1.5 wt% of rhodium. Both supports present moderate and strong acid sites. For the selective opening of decalin, the best metal/support combination was found with Rh(1.5)/SIRAL 70 balancing the support acidity together with the hydrogenolytic activity of the metal. A linear correlation was established between the amount of coke deposited and the formation of dehydrogenated compounds.