Bimetallic Ni-Mo catalysts deposited on alumina show unusual properties when used in the steam reforming of hydrocarbons. An introduction of small amounts of molybdenum compounds (less than or equal to 0.1 wt.-%) considerably reduces the detrimental effect of carbon deposit formation and increases the activity of methane steam reforming. With larger amounts, one observes a decrease in the catalyst activity, although it is much smaller than the reduction of the coking rate. The properties of the Ni-Mo/Al2O3 catalysts depend on the hydrogen-steam ratio in the reaction mixture which affect the mean degree of oxidation and distribution of various molybdenum states on the surface.