LaCoO3, Co3O4 and a mix of them, were synthesized and studied in the case of automotive exhaust reactions. Two preparation methods were used : simultaneous precipitation and a sol-gel type. The samples were characterised by X-ray diffraction. TPR, TPO and microanalysis. The CO oxidation reaction was performed under dry or wet atmospheres for a binary CO+O-2 and a complete CO+NO+C3H8+O-2 gas mixture. In all cases, the cobalt oxide pointed out the best performances. A quenching effect of the surface of the sol-gel catalysts induced activity at room temperature under the CO+O-2 dry mixture, Under the complete wet gasmixture, the perovskite LaCoO3 showed a lower activation energy for the CO oxidation reaction than for Co3O4.