Volatile organic compound (VOC) chemical sensors increasingly rely on the use of polymer nanocomposites (PNCs) as sensing materials, thanks to the simple processability of polymers combined with the conductivity properties of nanoparticles dispersed in an insulating polymer matrix. Recently, inkjet printing (UP), the main advantage of which is its patterning capability, was proven to be a reliable technique for the deposition of these materials. In this work, PNC chemical sensors were fabricated by UP of a polystyrene/carbon black based ink. The sensor responses were measured upon exposure to acetone vapors and analyzed as function of the sensitive material geometry. Among the different realized geometries, the lines transverse to the interdigitated electrodes fingers resulted in the optimal configuration for the sensing layer in a VOC chemical sensor. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 3644-3650, 2011