In a study on methanol decomposition over Cu based catalysts, it was found that the catalyst deactivation rate can be drastically reduced by adding CO2 in the feed. The enhancement of the catalyst stability was attributed to the retardation of catalyst sintering and carbon deposit on catalysts. However, the presence of CO2 did not alter the product distribution and initial catalyst activity. The results suggest a novel use of CO2 in methanol decomposition and a simple and efficient method to increase the stability of copper based catalysts.