Pt nanoparticles with controlled size of 1.5 and 6.5 nm were anchored onto the surface of WO₃ nanowires (WO₃NW) as well as on MCF-17 silica. In the case of WO₃NW and MCF-17 supported nanoparticles, 1.5 nm Pt nanoparticles were more active in ethanol decomposition reaction at 533 K. 6.5 nm Pt/WO₃NW catalyst showed ~6 times higher activity compared to MCF-17 supported 6.5 nm Pt nanoparticles. While MCF-17 supported catalysts produced hydrogen, methane, carbon-monoxide and acetaldehyde, the tungsten-oxide supported Pt nanoparticles produced a huge amount of acetone as well as ethene with a high acetaldehyde selectivity besides H₂, CH₄ and CO. The hydrogen formation was significantly higher when the Pt size was 1.5 nm. The metallic nanoparticles, the acid sites and the oxidized centers of support play important role in the formation of decomposition products of ethanol.