Two series of Mo and Fe containing catalysts have been prepared over alumina and titania supports using H3PMo12O40 heteropolyacid (HPMo) and Fe salt of HPMo. Catalysts have been characterized by BET, SEM, IR, TPR, XPS methods and by their HDS activity in the reaction of thiophene conversion. The TiO2-supported catalysts with low Mo concentration (6 wt%) show higher HDS activity than the catalyst with 12 wt% Mo. Iron promoting effect (Fe/Mo similar to 0.1) is observed with both, the alumina- and titania-supported catalysts. Iron supported over alumina increases Mo reducibility and decreases it on TiO2-supported catalysts. Compared to alumina-supported catalysts, the TiO2-supported catalysts show higher surface concentration of Mo6+ and Mo5+ in octahedral coordination - Mo(Oh). Iron increases the Mo(Oh) concentration even more. After sulfidation the Fe-containing catalysts show formation of different Mo valence states (Mo4+, Mo5+, Mo6+), Fe-P, Mo-P and/or Fe-Mo-P bonds, which affect the HDS catalytic activity.