The activity of the vanadium magnesium binary oxides supported on C-act, SiO2, gamma-Al2O3 and ZnO in the dehydrogenation of isobutane to isobutene under the carbon dioxide or inert gas atmosphere was investigated. The highest isobutene yield (34.8%) was obtained over active carbon supported catalyst. The role of carbon dioxide in the dehydrogenation process was determined on the basis of additional tests: the RWGS reaction, gasification of coke and regeneration of partially reduced catalysts. The temperature-programmed techniques (TPR-H-2, TPD-NH3 and TPD-CO2) were used to characterize the catalysts.