A study of the surface and gas-sensitive properties of In2O3 films modified with gold nanoparticles and synthesized by the successive ionic layer deposition (SILD) method was conducted. In2O3 films were prepared using the spray pyrolysis method. The gas-sensing characteristics were tested using CO, H-2, and O-3 as target gases. It has been shown that the surface modification with gold nanoparticles gives the opportunity to optimize the response of In2O3-based gas sensors to both reducing (CO, H-2) and oxidizing (O-3) gases. It has been found that the sensitizing effect during ozone detection was significantly higher than the effect during CO and H-2 detection. It has been demonstrated that the sensitizing effect depended on the number of SILD cycles used for gold nanoparticle deposition and was maximal for the In2O3 surface decorated with gold nanoparticles with the smallest size. The mechanism of the gold nanoparticles' influence on the gas-sensing properties of the In2O3 films is also discussed. It is suggested that to explain the observed effects, we have to consider both the "electronic" and "chemical" mechanisms of sensitization. Suggestions for studies to be carried out to further improve both the understanding of the nature of the gas-sensitive effects and the parameters of In2O3:Au-based gas sensors are also formulated. (C) 2016 Elsevier B.V. All rights reserved.