cis-1,4-Dinitroglycoluril (1,4-dinitrotetrahydroimidazo[4,5-d]imidazole-2,5-(1H,3H)-dione, C4H4N6O6, known as DINGU in the literature) is an important explosive regarded as one of the potential ingredients for LOVA (low vulnerability ammunition) applications. However, there is no study concerning trans-DINGU, to the best of our knowledge. Thus, in the present study the structural and electronic properties of the configurational isomers of DINGU (cis- and trans-isomers) have been investigated by performing density functional theory (DFT) calculations at B3LY-P/6-31G(d,p), UB3LYP/6-31G(d,p) levels and also ab initio calculations at RHF/6-31G(d,p) and UHF/6-31G(d,p) levels. The optimized geometries, vibrational frequencies, electronic structures, and some thermodynamical values for the presently considered DINGU isomers have been obtained in their ground states. Comparing the calculated energy data (total electronic energy, heat of formation values and homolytic bond dissociation values of N-NO2) and the calculated bond lengths, cis-DINGU was found to be a more stable molecule than the trans-isomer. (c) 2006 Elsevier B.V. All rights reserved.