Series of CoMo-based carbon catalysts were synthesized via the successive impregnation method, in which the carbon material was impregnated first with cobalt. The activity of the catalysts in the hydrodesulfurization of dibenzothiophene using a high pressure batch reactor operating at 340 degrees C under 3 MPa of hydrogen was investigated. in general, the carbon-supported CoMo catalysts synthesized by the successive impregnation method (in this case cobalt was the first to be introduced) showed higher hydrodesulfurization activities for dibenzothiophene than the reference CoMo-based carbon catalyst prepared by the conventional successive impregnation. The remarkable hydrodesulfurization activities of these CoMo-based carbon catalysts are suggested to be a consequence of forming a new synergy between molybdenum and cobalt. The data provide evidence that the CoMo-bimetallic synergy is affected by the nature of the support and by the order of metal impregnation. The results support the view of the electronic origin of such synergy. (c) 2008 Elsevier B.V. All rights reserved