The CO2/CH4 ratio during methanation on Pt was found to be very sensitive to the proximity of Pt and CeO2. On 0.6 wt% Pt/Al2O3, the CO2/CH4 ratio was almost-equal-to 0.09 suggesting that most of the 0 from the CO ends up as H2O in the product stream. In contrast, on 0.6 wt% Pt/CeO2 the CO2/CH4 ratio ranged from 0.8-1.0. The selectivity to CO2 was not a result of the sequential water-gas shift reaction nor was it caused by a surface reduction of CeO2 by CO. The highest selectivity to CO2 is observed on catalysts with the smallest Pt particle sizes, providing further evidence that Pt-CeO2 contact influences the selectivity toward CO2 formation. In this study, we have also investigated whether the CO2/CH4 ratio could be used as a probe of Pt-CeO2 contact in Pt/CeO2-Al2O3 catalysts.