Tungsten-trioxide (WO3) and lanthanum oxide (La2O3)-added WO3 nanoparticles were successfully prepared by sol-gel method. The structure and morphological characteristics of the nanopowders were studied by means of field-emission SEM (FE-SEM). The results showed that all the nanopowders of spherical shape with average size smaller than 40 nm have good dispersivity. The effect of La2O3 on the gas response of the samples was investigated, especially the volatile organic compound (VOC) gases. The highest gas response of La2O3-added WO3 is found to shift to low temperature, compared to that of the pure WO3. Analysis with FE-SEM revealed that, compared with the pure WO3, La2O3-added WO3 has a smaller average grain size but greater surface area. Complex impedance spectroscopy analysis indicated an increase in grain boundary resistance. (c) 2008 Elsevier B.V. All rights reserved.