The hydro-dehydrogenation of cyclohexene has been studied on: alumina supported Co-, Ni-, Pd-, Pt-promoted and non promoted MoOx, monometallic Co, Ni and Pt, two - alumina and silica-alumina supported - Ni-promoted WOx-s. Two groups of characteristically different catalytic behavior of the promoted MoOx and WOx samples were identified dependent of the presence and nature of the zerovalent metal on the catalyst surface. No additivity of activities but some interaction between metals and oxides was expressed in the catalytic behavior of the M(8-10)MoOx catalysts.