This paper reports the effect of selective tin addition to nickel catalysts via a controlled technique (surface organometallic chemistry on metals, SOMC/M), and the performance of the resulting systems in methane reforming processes: partial oxidation (POM), CO2 reforming (R) and mixed (CO2 + O-2) reforming (MR), with particular emphasis on their resistance to coke formation. It is demonstrated that SOMC/M techniques allow to obtain well-defined bimetallic phases in a controlled way. It is found that there is a range of tin concentrations (0.01-0.05 wt.%) for which the stability of the bimetallic catalysts is markedly enhanced with respect to nickel catalyst, without affecting either the activity level or the selectivity to syngas. These facts are explained in terms of a more demanding nature in size of the active sites needed for carbon formation reaction, when compared to methane activation reaction to synthesis gas.