Pure and Pd-doped ZnO nanofibers were synthesized by electrospinning method, and characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The diameters of the fibers annealed at 600 degrees C range from 70 to 160 nm. Compared with pure ZnO nanofiber sensor, the Pd-doped ZnO nanofiber sensor exhibits improved sensing properties to CO at 220 degrees C. Moreover, this sensor processes considerable sensitivity to low concentration CO in the range of 1-20 ppm with good selectivity. The response and recovery times are in the range of 25-29 s and 12-17 s, respectively. The sensing mechanism is also discussed. (C) 2010 Elsevier B.V. All rights reserved.