This Letter deals with the assignment of photoluminescence (PL) emission spectra of SrTiO3. Ideal and distorted structures of SrTiO3 model systems have been selected to localize and characterize at DFT calculation level both ground (singlet) and excited (triplet and singlet) electronic states. This study provides clear evidence of the role carried out by stable electronically excited states, and their relationship with order-disorder effects as a key component of the PL behaviour. (C) 2010 Elsevier B. V. All rights reserved.