The model RhOx/CeO2 systems were prepared by radio-frequency (RF) plasma sputtering of Rh electrode in O2 or Ar/O2 atmosphere. Thermal stability of the systems and their reaction probability towards CO oxidation were studied by X-ray photoelectron spectroscopy. It was shown that the small oxidized Rh nanoparticles on the CeO2 surface (RhOx/CeO2) obtained by RF sputtering in O2 have spectroscopic characteristics close to those of Rh3+ ions highly dispersed in ceria lattice. The RhOx/CeO2 system remains stable upon heating in vacuum at 450°C and shows reactivity towards CO oxidation at T > 200°C. RF sputtering in Ar/O2 atmosphere results in the formation of larger rhodium nanoparticles that are close to Rh2O3 oxide. The Rh2O3/CeO2 system demonstrates lower activity in CO oxidation and cannot be reduced at a temperature below 300°C.