The influence of mesoporous materials on the properties and HDS activity of Mo and NiMo catalysts was investigated for supports containing 50 wt.% of MCM-41. A series of catalysts was characterized by different techniques (S-BET, TPD-NH3, TPR, SEM, XPS) and tested in dibenzothiophene (DBT) conversion. On the surface of the catalysts containing mesoporous materials, agglomerations of the Mo oxo-species were observed. The presence of MCM-41 in the support visibly weakened the promoting effect of TiO2 on the reducibility of Mo oxides. The results of DBT HDS showed that the NiMo catalyst supported on MCM-41 was not only less efficient than that supported on Al2O3 but also that supported on Al2O3-TiO2. From the distribution of DBT HDS products we can conclude that over catalysts containing MCM-41 the desulphurization of DBT runs mostly via the DDS route. (c) 2006 Elsevier B.V. All rights reserved.