In this work, we explore the validity of the application of the constrained density functional theory (CDFT) to the study of intramolecular charge transfer reactions. Accordingly, we carry out single-point calculation using CDFT and MRMP2 at each point in the intramolecular charge-transfer reaction coordinate of 1,3-dinitrobenzene anion radical, calculated using the complete active space self-consistent filed theory (CASSCF). We show that the CDFT//CASSCF and MRMP2//CASSCF energy profiles are qualitatively and quantitatively similar. Therefore, we conclude that CDFT is a good tool for studying the intramolecular charge-transfer reactions. (C) 2011 Elsevier B. V. All rights reserved.