The effects of preparation process and starting material on hydrodesulfurization (HDS) activity of alumina supported ruthenium, molybdenum and ruthenium-molybdenum hydrotreating catalysts were investigated. Conventional impregnation method and gradual gas phase adsorption were compared as a preparation route. The HDS tests showed that controlled gas phase deposition is advantageous in the preparation of the monometallic catalyst systems. The most promising HDS activity was achieved with the RuMo/Al2O3 catalyst prepared from binuclear organometallic complex. This suggests that the direct ruthenium-molybdenum bond in the structure of the catalyst precursor favors the formation of highly active surface phase. The oxidation and reduction behavior of the catalysts was studied by oxygen pulse chemisorption (PCO) and temperature programmed reduction (TPR), A clear relationship was observed between the method of preparation and the reactivity of the surface species.