In the approximation of the time-dependent electron density functional theory (TDDFT) we have studied using the quantum-chemical method the nature of excited states of 2-βdiketonato-1,3,2-benzodioxaboroles. The substituents are one or two phenyl cycles in β-position of diketonate group. I. PheO2B(AA) R1=R2=CH3 II. PheO2B(BA) R1=CH3, R2=C6H5 III. PheO2B(DBM) R1=R2=C6H5 Optimization of geometry for these spiroborates leads to perpendicular positions of two planes connected with B atom. Based on the calculated transition energies and oscillator strengths, we have simulated the absorption spectra in the ultraviolet and visible region. The calculated absorption spectra have been compared with the experimental spectra measured in acetonitrile solutions using Shimadzu UV-2550 spectrophotometer. The shift of main absorption band from 287 nm (I) to 368 nm (III) is in agreement with the shift obtained from calculations. As the π system becomes more extended, a bathochromic shift of the absorption band and an increase in the transition probability are observed. The calculations show there are two low-energy transitions of π-π type which are formally allowed by symmetry. They are charge-transfer transitions from dioxyphenyl group to chelate group. First of them have a vanishing oscillator strength and probably cannot be measured experimentally. Second of them has noticeable oscillator strength and is attributed to the observable long-wave shoulder on the main band. The π-π transitions which have usual high oscillator strength form some bands of high intensities in the ultraviolet region of spectra. The ππ transitions within the chelate-phenyl fragment give the most contribution into this region. These modeled structures are in agreement with measured spectra. The comparison with the absorption spectra of F2B(AA), F2B(BA), F2B(DBM) [1,2] which have not a dioxyphenyl group was made. The increase of red shift of main band when increasing of number of phenyl fragments suggests that a weak interaction exists between dioxyphenyl and phenyl groups in the spiroborates.