Oxidative dehydrogenation (ODH) of isobutane over LaBaSm oxide catalyst in the temperature range 450-600 degrees C, and the influence of the addition of CO2 into the feed were investigated. It was found that LaBaSm oxide is an active and stable catalyst for ODH of isobutane. Upon reaction conditions the specific surface area decreases and a new phase, La2O(CO3)(2), is formed, which causes an increase in the surface specific conversion. The selectivity to isobutene as well as isobutane conversion can be improved by adding CO2 into the feed. These effects may be explained as due to the combined effects of improvement of the active phase formation and the competition between molecular O-2 and CO2 adsorption on the sites which are responsible for total oxidation.