Three NiMo sulfided catalysts with the same active phase content and deposited on different supports (alumina, silica-alumina and alumina-Y zeolite) were prepared aiming to obtain bifunctional catalysts with different acidities and good dispersion of the sulfide phase for analyzing the role of the support acidity on the hydrogenation and hydrocracking activities for the conversion of tetralin. Support acidity promotes the ring opening of tetralin, increasing the yields of aromatic compounds among the reaction products of silica-alumina and alumina-Y zeolite supported catalysts. However, these catalysts also presented high activities for both ring opening/cracking and hydrogenation reactions, respectively associated to the support and to sulfided metal phase, as compared to alumina supported one, which presented essentially hydrogenated products. Although the hydrogenation activity of sulfided catalysts can be modified by neighboring acid sites, the complex reaction network for the tetralin conversion, involving series and parallel steps on both acid and hydrogenation sites, has to be taken in account for explaining the present results. (C) 2010 Elsevier BM. All rights reserved.