For the first time nitrogen or boron doped carbon nanotubes were added into a SnO2 matrix to develop a new hybrid CNTs/SnO2 gas sensors. The hybrid sensor is utilised to detect low ppb concentrations of NO2 in air, by measuring resistance changes of thin CNTs/SnO2 films. The tests are performed at room temperature. For comparison, pure SnO2 and N or B-substituted CNT sensors are also examined. Comparative gas sensing results reveal that the CNTs/SnO2 hybrid sensors exhibit much higher response towards NO2, at least by a factor of 10, and good baseline recovery properties at room temperature than the blank SnO2 and the N or B-substituted CNT sensors. This finding shows that doping SnO2 with low quantity of CNTs doped with heteroatoms can dramatically improve sensitivity. (C) 2011 Elsevier B.V. All rights reserved.