The use of zeolites as transformation layers to enhance the response and discriminating power of solid-state metal-oxide-semiconductor gas sensors is demonstrated. Thick film sensors were prepared by screen printing layers of tungsten trioxide or chromium titanium oxide with various zeolites as overlayers. The sensors gas response was tested against carbon monoxide and ethanol in varying concentrations. Experimental result.,; show that it is possible to dramatically alter the response behavior of the devices: in the instance of ethanol gas with a zeolite Y-modified sensor. the response was increased by 2 orders of magnitude compared to the unmodified sensor. Computational modelling studies show that a combination of catalytic reaction and diffusion behavior are responsible for these changes. Such discriminatory behavior should prove useful in electronic noses and sensor arrays. (c) 2009 The Electrochemical Society. [DOI: 10.1149/1.3065436] All rights reserved.