Peroxo vanadium complexes represent synthetic structural and functional models for the peroxo form of the vanadium haloperoxidase enzymes and can exhibit insulin mimetic properties or antitumor activity. These complexes also represent intermediates in the catalytic cycle of the vanadium haloperoxidase reactions and can be used as catalysts for oxygen transfer reactions. The aim of the present communication is modeling of the UV-Vis and IR spectra of the [VO(O2)Hheida]- complex dissolved in water and assignment of the observed bands. First the optimization of the structure of the  complex, calculation of its vibrational frequencies as well as of the transition energies and absorption profiles have been performed within the frames of DFT with the aid of the ORCA package [1]. Secondly, the absorption spectrum of the [VO(O2)Hheida]- complex was calculated in the approximation of “strong heat release” [2], when the shape of an individual s→p transition is described by a Gaussian curve. In the latter case the parameters m ps, 2 p and 2 psd determining the maximum, width and oscillator strength of the absorption band on this transition were taken from DFT calculations as well. It was obtained that the absorption curves of the [VO(O2)Hheida]-  complex calculated within the ORCA package  and  in  the  approximation of   strong heat release coincide when in the former case the individual linewidths p  are taken broader than 1000 cm-1. It has been also revealed that the maxima of the absorption band in the violet and visible ranges correspond, respectively, to the electron transfer from the terminal oxygen and the peroxo group to the V ion.  For the [VO(O2)Hheida]- complex dissolved in water the IR spectrum in the range 400 -1100 cm-1 has been examined as well. The calculated positions, intensities and the grouping of vibrational frequencies in the NIR spectra are in satisfactory agreement with the observed ones.