RuO2/SnO2 catalysts with 2, 5 and 10 % Ru loadings were prepared with calcined and uncalcined SnO2 supports by the impregnation method. The catalysts were evaluated for CO and CH4 oxidation and characterised by N2-BET, XRD, hydrogen temperature programmed reduction (H2-TPR), energy-dispersive X-ray spectroscopy scanning electron microscopy (EDS-SEM) and thermogravimetric analysis differential scanning calorimetry (TGA-DSC). Owing to the synergetic effect between RuO2 and SnO2, all RuO2/SnO2 catalysts are found to be much more active than pure SnO2 and RuO2/Al2O3 for both CO and CH4 oxidation. For RuO2 supported on uncalcined SnO2, H2-TPR and TGA-DSC analysis revealed the formation of a new, less active compound between Sn and Ru that consumed active SnO2 and RuO2, and could be detrimental to the synergism between RuO2 and SnO2, and thus the activity of RuO2/SnO2 catalytic system. As a consequence, it is much less active than RuO2 supported on calcined SnO2. RuO2/SnO2 catalysts are also very stable in the presence of water vapour, which gives them potential for application in after-treatment processes.