In this work, we compare the performance characteristics of two different zinc oxide films layered on a quartz crystal microbalance (QCM) as gas-sensing elements. The films were prepared by different methods, i.e., RF sputtering on a QCM surface and drop-casting a colloid of ZnO nanoparticles generated via laser ablation in liquid. Prior to use, both films were characterized in terms of their surface morphology and chemistry, after which their gas sensing properties were evaluated by using the QCM method. The film prepared from a laser-generated material was much more porous than its sputtered counterpart. Gas sensing of ethanol using the QCM coated with the two films showed that the sensing response differs depending on the state of the detection film. This demonstrated that there is a correlation between the surface characteristics and the gas adsorption characteristics of the sensors based on two different ZnO materials.