The influence of hollowness variations on the gas-sensing performance of ZnO hollow fibers (Hfs) was investigated by varying their hole diameter. The hole diameter of the ZnO Hfs was changed using template polymer fibers with various diameters, which were synthesized by electrospinning. Hfs with smaller hole diameters were more sensitive to both reducing and oxidizing gases than those with larger diameters. The improved gas-sensing ability was attributed to the increased surface area of the Hfs due to the smaller hole diameter. The results show that the hole diameter is a key shape parameter and should be accurately monitored to maximize the gas-sensing properties of Hfs; thus, in this paper an important guideline for the use of oxide Hfs in chemiresistive-type gas sensors is provided. (C) 2016 Elsevier B.V. All rights reserved.