Carbon nanotubes (CNTs) are relatively potential materials for catalyst supports. CNT-supported Cu catalysts were prepared by an impregnation method and a polyol process. The catalytic activity was examined under different reaction atmospheres, Cu contents, and sizes of supports for CO oxidation. The experimental results showed that the active phase on the catalyst prepared by the impregnation method (10-20 nm) was smaller than that on the catalyst prepared by the polyol process (30-50 nm). Furthermore, the smaller active phase showed better performance for CO oxidation. Therefore, catalysts prepared by the impregnation method had a lower activation energy (57.47 kJ mol(-1)) than those prepared by the polyol process. The optimum CNT-supported Cu catalyst prepared by the impregnation method using 10-20 nm CNTs had a Cu content of 13.4 wt.%, and a CO conversion of 33% achieved at 125 degrees C with a total space velocity of 1.56 x 10(5) h(-1). (c) 2008 Elsevier B.V. All rights reserved.