The dehydrogenation of ethylbenzene over alumina-supported vanadium-antimony oxide catalyst has been studied under different atmospheres such as inert nitrogen, steam, oxygen and carbon dioxide as diluent or oxidant. Among them, the addition of CO2 gave the highest styrene yield (up to 82%) and styrene selectivity (up to 97%) along with stable catalytic performance. Carbon dioxide plays a beneficial role as a selective oxidant in improving the catalytic behavior through the oxidative pathway. (c) 2005 Elsevier B.V. All rights reserved.