In this work, palladium (Pd) thin films were prepared via RF sputtering method with various thicknesses (6 nm, 20 nm and 60 nm) on both a flexible substrate and a hard substrate. Hydrogen (H-2) sensing properties of Pd films on flexible substrate have been investigated depending on temperatures (25-100 degrees C) and H-2 concentrations (600 ppm - 10%). The effect of H-2 on structural properties of the films was also studied. The films were characterized by Scanning Electron Microscopy (SEM) and X-ray diffraction. It is found that whole Pd films on hard substrate show permanent structural deformation after exposed to 10% H-2 for 30 min. But, this H-2 exposure does not causes any structural deformation for 6 nm Pd film on flexible substrate and 6 nm Pd film on flexible substrate shows reversible sensor response up to 10% H-2 concentration without any structural deformation. On the other hand, Pd film sensors that have the thicknesses 20 nm and 60 nm on flexible substrate are irreversible for higher H-2 concentration (>2%) with film deformation. The sensor response of 6 nm Pd film on flexible substrate increased with increasing H-2 concentration up 4% and then saturated. The sensitivity of the film decreased with increasing operation temperature. (C) 2016 Elsevier B.V. All rights reserved.