Ruthenium catalysts supported on the mesoporous carrier MCM-41 were synthesized and characterized. It was found that the presence of the metal markedly accelerated decalin ring opening reactions as compared to the acid support alone, and it increases the selectivity owing to inhibition of protolytic cracking. It was shown that activity of ruthenium catalytic systems is lower than that of platinum catalysts supported on MCM-41 and much lower than the activity of platinum on zeolites. The low activity of catalytic systems based on the mesoporous support MCM-41 is due to its substantially lower acidity in comparison with zeolites beta and Y. Thus, it is concluded that the use of MCM-41 in decalin ring opening reactions is limited even in the presence of the metal, first of all, because of the low acidity of the support.