Semiconductor (Pd-doped SnO2) gas sensors covered with zeolitic films (MFI or LTA) have been developed and used for gas phase sensing of different species (methane, propane, and ethanol) at different humidity levels. The dynamic responses obtained with these sensors were compared with the response of a reference sensor without a zeolitic layer. The results clearly indicate that a suitable zeolite layer strongly reduces, and in some cases suppresses, the response of the sensor to paraffins, thereby increasing the sensor selectivity to the alcohol, while the reference sensor could not discriminate between these molecules. This clearly shows the potential of zeolite-based sensors to achieve a higher selectivity/sensitivity in gas sensing applications. (C) 2003 Elsevier B.V. All rights reserved.