Using HF and DFT-B3LYP methods, basis set dependence on the optimal geometry of tris(o-phenylenedioxy)cyclotriphosphazene has been investigated. It was found that polarized functions are necessary for an appropriate description of geometry characteristics and electronic structure of this compound. B3LYP/6-31G(d) optimized geometry was found to agree well with crystal data. The study of the electronic structure of the neutral molecule has shown that the frontier orbitals are strongly localized on the three spirocyclic side groups, while injection effect of charge on the structure of the molecule has small structural changes on it, implying a certain stability of the molecular structure. (C) 2004 Elsevier B.V. All rights reserved.