Monocrystal matrices of high-gap oxides are finding increasing applications as hosts of luminescent ions, typically rare earths (RE)s. Currently, RE-doped oxyorthosilicates, aluminum perovskites, and garnets (RE(2)SiO(5)-REAlO(3)-RE(3)Al(5)O(12)) are widely used as highly efficient and fast scintillators for gamma-ray detection. On the other hand, shallow or deep intragap energy levels, due to stoichiometric deviation or impurities unintentionally added in the crystals, play a counteractive role giving rise to slower scintillation decay time, reduced light yield and afterglow. The aim of this work is to show how it is possible to tailor these unwelcome outcomes and RE-ion interactions for engineering new devices for optical memory storage. In this sense, experimental results of thermo- and radio-luminescence are presented. The role of the bandgap and the location in energy of the levels due to the RE dopants and to the defects is discussed from a theoretical point of view. The feasibility in the near future of new promising transparent displays is also discussed. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim