Multi-walled carbon nanotubes (MWCNTs) were successfully coated with tin-dioxide (SnO2) nanoparticles using both hydrothermal process and sol–gel technique under different solvent conditions. The obtained MWCNTs/SnO2 nanocomposites had the weight ratio of the components 1:4, 1:8 and 1:50, respectively. The as-prepared nanocomposites were characterized in detail using scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). Gas-sensor structures are developed on the base of these materials. High response to methanol and ethanol vapour as well as i-butane gas at 200 °C operating temperature has been revealed for the functionalized with Ru nanocomposite thick-film sensor structures having the ratio of the components 1:8 and 1:50. The structures having 1:4 ratio of components exhibit the best selectivity toward methanol and ethanol vapors.