The effect of the addition of small amounts of rare earths(Ln=La, Ce, Nd and Gd) to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was investigated. Samples of Ln/Cu Co/Al catalyst were prepared and characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), atomic absorption spectroscopy(AAS), scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS), H2-temperature-programmed reduction(H2-TPR), electron paramagnetic resonance(EPR) spectroscopy and low temperature nitrogen adsorption. The results showed that the addition of rare earths changed the surface state of the alumina supported copper-cobalt spinel catalyst. As a result, partial reduction of copper species was observed as well as migration of these species between the surface and the bulk. The Ln/Cu Co/Al catalysts behaved differently in oxidation and reduction processes. In oxidation processes where oxide structure was important, Ce/Cu Co/Al and Nd/Cu Co/Al were the most active catalysts. The catalyst Ce/Cu Co/Al was the most active in the oxidation reactions because of the availability and favorable surface distribution of the redox couples Cu+/Cu2+ and Ce3+/Ce4+. In NO decompostion, Ln-modified catalysts significantly improved the selectivity of the process to N2. The effect of the addition of small amounts of rare earths (Ln = La, Ce, Nd and Gd) to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH4 oxidation and in NO decomposition was investigated. Samples of Ln / Cu Co / Al catalysts were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), scanning electron microscopy-energy dispersive spectroscopy -programmed reduction (H2-TPR), electron paramagnetic resonance (EPR) spectroscopy and low temperature nitrogen adsorption. The results showed that the addition of rare earths changed the surface state of the alumina supported copper-cobalt spinel catalyst. Reduction of copper species was observed as well as migration of these species between the surface and the bulk. The Ln / Cu Co / Al catalysts behaved differently in oxidation and reduction processes. In oxidation processes where oxide structure was imp ortant, Ce / Cu Co / Al and Nd / Cu Co / Al were the most active catalysts. The catalyst Ce / Cu Co / Al was the most active in the oxidation reactions due of the availability and favorable surface distribution of the redox couples Cu + / Cu2 + and Ce3 + / Ce4 +. In NO decompostion, Ln-modified catalysts significantly improved the selectivity of the process to N2.