Epitaxial films of Ce-doped Gd-3(AlxGa1-x)(5)O-12 with x = 0.00, 0.22, 0.31, 0.38 formula units were grown using liquid-phase epitaxy method, and their optical properties were studied. The emission of Ce3+ ions can be observed only when Al3+ ions are incorporated into the garnet structure, resulting in a shift of the 5d Ce3+ states from the conduction band to the bandgap. It is shown that the shift is caused by the cumulative effect of gradual low-energy shift of the lowest 5d level of Ce3+ and the raise of the garnet bandgap energy with increasing Al3+ concentration. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.