A series of Rh-Mo/ZrO2 catalysts with fixed Rh and different Mo loadings were prepared and characterized by H-2 chemisorption, XRD, TPR, TEM and XPS. The catalysts were studied in two reactions : the hydrogenation of carbon monoxide and the hydrogenation of toluene. The results suggest that the increase in the Mo content produces a partial coverage of the support and the Rh particles. Moreover, at high Mo coverage, an increase of the MoO3 layer thickness is produced. After being treated in hydrogen, the molybdenum oxide remains as slightly reduced particles, while Rh is essentially as Rh-0, with only a small contribution of Rh+ species. The Mo promotes the formation of oxygenates in the CO hydrogenation and it does not affect the activity in the hydrogenation of toluene.