The influence of the Bronsted acidity, SiO2/Al2O3 ratio and Rh-Pd content on the ring opening of decalin was studied. Rh- and Pd-based monometallic and bimetallic catalysts were prepared by impregnation on three commercial SiO2/Al2O3 supports (SIRAL 5, 20 and 40). The catalysts were characterized by TPD of pyridine, X-ray diffraction, H-2 chemisorption, isomerization of 3,3-dimethyl-1-butene (33DM1B) and selective ring opening (SRO) of decalin. It was found that the support acidity is strongly influenced by the SiO2/Al2O3 ratio, the SIRAL 40 being more acid. The metal accessibility has the following order: supported catalysts on SIRAL 40 > SIRAL 20 > SIRAL 5. The incorporation of Rh and/or Pd modifies the conversion and the product distribution on decalin reaction. The support acidity has a strong influence on the conversion and product distribution on the decalin reaction at 350 degrees C, SIRAL 5 series have low selectivity to RO and high selectivity to dehydrogenated compounds. On the other hand, SIRAL 40 series lead to the highest yield to cracking products of the three studied series. Catalysts with Rh/Pd atomic ratios equal to 2 and monometallic Rh1 supported on SIRAL 40 are the most active and selective catalysts to ring opening products