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Crystalline Cd(OH) 2 /CdCO 3 nanowires, having lengths in the range from 0.3 up to several microns and 5-30 nm in diameter, were synthesized by a microwave-assisted wet chemical route and used as a precursor to obtain CdO nanostructures after a suitable thermal treatment in air. The morphology and microstructure of the as-synthesized and annealed materials have been investigated by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and thermogravimetry-differential scanning calorimetry. The change in morphology and electrical properties with temperature has revealed a wire-to-rod transformation along with a decreases of electrical resistance.Annealed samples were printed on a ceramic substrate with interdigitated contacts to fabricate resistive solid state sensors. Gas sensing properties were explored by monitoring CO 2 in synthetic air in the concentration range 0.2-5 v/v% (2000-50 000 ppm). The effect of annealing temperature, working temperature and CO 2 concentration on sensing properties (sensitivity, response/recovery time and stability) were investigated. The results obtained demonstrate that CdO-based thick films have good potential as novel CO 2 sensors for practical applications.