Impact of post-growth thermal treatment parameters (temperature, duration, atmosphere composition) on optical, luminescent, and scintillation characteristics of Lu2xGd2-2xSiO5:Ce LGSO:Ce has been analyzed. Absorption, X-ray luminescence spectra, thermostimulated luminescence curves, as well as light yield and energy resolution, have been measured before and after thermal treatment in different regimes. Scintillator optimization by thermal treatment allows to improve the energy resolution up to 6.7% at 662 keV. (C) 2014 Elsevier Ltd. All rights reserved.