In this work we have synthesized single crystallyne In₂O₃ nanocubes by means of a hydrothermal method at low temperatures followed by calcination at different temperatures. Oxidising and reducing gases such as NO₂ and CO have been tested and the optimum working conditions for each gas have been found. An excellent response at trace levels could be obtained at low operating temperatures for NO₂, which makes the sensor selective to this particular gas.