Carbon nanotubes (CNTs) have been fabricated by microwave plasma-enhanced chemical vapor deposition for detecting the presence of ethanol vapor. The conductance of the CNTs decreases when the sensors are successively exposed to ethanol vapor at room temperature. The surface of the CNTs was modified in oxygen plasma to elevate the detection sensitivity for ethanol. Successful utilization of CNTs in gas sensors may open a new window for the development of novel nanostructure gas devices. (c) 2008 Elsevier B.V. All rights reserved.