Luminescent Ce3+-doped and Ce3+/Tb3+-codoped Y3Al5O12 powders and spray-coated films have been elaborated by the sot-gel technique. Their purity has been assessed by X-ray diffraction whereas X-ray Absorption Spectroscopy has evidenced the partial oxidation of Ce3+ into Ce4+ in samples containing or not Tb3+. Film thicknesses have been determined by profilometry. Powder and film morphology has been studied using Scanning Electron and Transmission Electron Microscopies, evidencing nanostructured well-densified phosphors. Scintillation properties of both kinds of samples have been investigated upon X-ray radiation and optimal cerium concentration has been determined for crystallized powders. Substitution of one part of yttrium ions by terbium ions in Y3Al5O12:Ce samples has entailed a significant enhancement of scintillation efficiency for both powders and films. These improvements will be discussed regarding in particular the changes in the X-ray absorption by photoelectric effect related to the matrix modification. In addition to this enhancement, emission maximum of co-doped samples is red-shifted to 544 nm, that matches more suitably with the optical photon detectors used in X-ray imaging. (C) 2011 Elsevier B.V. All rights reserved.