Ni/La2O3 and Ni/Al2O3 catalysts were studied under conditions of partial oxidation of methane to synthesis gas. Temperature-programmed oxidation and hydrogenation experiments have shown that carbon accumulation over Ni/La2O3 during CPO remains essentially constant after 2 h time on-stream, while over Ni/Al2O3 it increases during the initial several hours. FTIR spectroscopy of surface species formed over the Ni/La2O3 catalyst under reaction conditions indicates that the carbonate species formed over the support do not decompose under He and O-2 treatment at 600 degrees C. XRD spectra obtained following high (similar to 90%) or low (<10%) methane conversions show that Ni, La2O3, La2O2CO3, NiO, and Ni3C phases are present in the case of high methane and complete oxygen conversions, while nickel oxide, nickel carbide and, to a small extent, La2O2CO3 phases are present in the case of low CH4 and incomplete oxygen conversions.