CoMo/gamma-Al2O3 catalyst containing 16.0 wt% MoO3 and 3.2 wt% CoO was prepared by equilibrium deposition filtration method (EDF). The CoMo oxidic catalyst was characterized by elemental analysis, N-2 adsorption, XRD, and TPR. The sulfided catalyst was characterized by FTIR of adsorbed CO at 30 degrees C. Hydrodesulfurization (HDS) and hydrodearomatization activities were evaluated for heavy gas oil (HGO) in a trickle bed reaction system using the following conditions: reaction temperatures of 340, 360, 380 and 400 degrees C, a reaction pressure of 20, 35, 50 and 65 bar, a liquid hourly space velocity (LHSV) of 1.0, 1.5, 2.0, 2.5 and 3 h(-1) and a H-2/feed ratio of 400 L L-1. The experimental results were used to determine apparent reaction orders and activation energies. The dispersion, nature of active sites and hydrotreating activity of this catalyst were compared with the conventionally prepared CoMo/gamma-Al2O3 catalyst containing similar wt% of MoO3 and CoO. The CoMo catalyst prepared by equilibrium deposition filtration method has higher HDS and HDA rate constants than the conventional catalyst due to an improved dispersion of MoS2. (C) 2010 Elsevier Ltd. All rights reserved.