The present invention relates to a catalyst comprising 0.1-10 mol % Co3-xMxO4, where M is Fe or Al and x=0-2, on a cerium oxide support for decomposition of N2O in gases containing NO. The catalyst may also contain 0.01-2 weight % ZrO2. The invention further comprises a method for performing a process comprising formation of N2O. The N2O containing gas is brought in contact with a catalyst comprising 0.1-10 mol % CO3-xMxO4, where M is Fe or Al and x=0-2, on a cerium oxide support, at 250-1000.degree. C. The method may comprise that ammonia is oxidized in presence of an oxidation catalyst and that the thereby formed gas mixture is brought in contact with the catalyst comprising the cobalt component on cerium oxide support at a temperature of 500-1000.degree. C.