We doped (M) and codoped (MM') Co, Cu, and Ni into CeO2 support, and tested their gas-phase CO oxidation performance by temperature-programmed reaction mass spectrometry for the as-prepared, thermal H-2- and N-2-treated samples. Additionally, fundamental characteristics of doped CeO2 were revealed by transmission electron microscopy, optical microscopy, X-ray diffraction crystallography, UV-visible absorption, Brunauer-Emmett-Teller (BET) surface area measurements, and temperature-programmed reduction experiments. The CO oxidation performance was greatly improved upon metal-doping and thermal pre-treatment in H-2 and N-2 condition. It was found that Cu-contained samples showed higher CO performance while Ni, Co and CoNi-doped samples showed poor performances. The T-10% (the temperature at 10% CO conversion) was lowered by 140 degrees C upon Cu-doping. Upon N-2 (or H-2-thermal treatment), the T-10% was lowered by 80 and 110 degrees C for Cu-doped and undoped CeO2 catalyst, respectively. Overall, this study provides deeper information of surface treatment effects useful to development of efficient catalysts. (C) 2014 Elsevier B.V. All rights reserved.