The dehydrogenation of propane to propene in the presence of CO2 over CrOX/SiO2 catalyst with a Cr content not exceeding the monolayer was investigated. The oxidative role of CO2 in this reaction was discussed on the basis of in situ DRS experiments in the 400-850 nm range. Fast reduction of the catalyst under propane/CO2 stream was observed by in situ diffuse reflectance spectroscopy (DRS) at 873 K.