Nickel based catalysts (15 wt.%) supported on a La-Sn mixed oxides (Sn/La atomic ratio = 1, 0.75, 0.5, 0.25 and 0) were prepared by a coprecipitation technique involving pH adjustment with KOH and then calcined at 950 degrees C. XRD analysis of the catalysts containing Sn showed the presence of the pyrochlore-like phase La2Sn2O7 and an intermetallic NixSny compounds as active phase. For the Sn/La ratios lower than 1, the formation of the perovskite-like phases La2NiSnO6 and LaNiO3 was also observed, with relative amounts in weight dependent of the Sn/La ratio, although they were easily destroyed under reaction conditions to form a more Sn-rich active phase. All the catalysts were active in the ethanol steam reforming at 650 degrees C with a production of a H2 and CO2 rich gas mixture. While the Sn presence in the catalyst decreases its catalytic activity, the formation of an intermetallic NixSny phase increases its resistance to the formation of carbonaceous residues and the presence of Sn+4 species in the pyrochlore compound promotes the WGSR decreasing the CO production. Carbonaceous residues on the spent catalysts were analyzed by TGA, EDS, Elemental Analysis and Raman Spectroscopy showing differences in their quantity and nature depending on the Sn/La ratio.