Highly dispersed CoMoS/Al2O3 was prepared by dispersing MoS2 crystallites on Al2O3 by a sonochemical method, followed by the selective deposition of Co on the resulting MoS2 crystallites. The newly prepared catalyst contained larger amounts of CoMoS phase, a known active site for hydrodesulfurization (HDS), than a catalyst prepared by sequential impregnation and, as a result, exhibited a two to three times higher activity than that of the impregnated one for the HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The former catalyst promoted hydrogenation (HYD) route to a greater extent than direct desulfulization (DDS) route. Therefore, the extent of activity increase for the new catalyst was larger for 4,6-DMDBT HDS, which proceeds largely via the HYD route, than for DBT HDS, which proceeds largely by DDS. © 2004 Elsevier B.V. All rights reserved.