A density functional theory (DFT) study of the V/UV spectrum and the adiabatic energy released from the triplet excited state of sapphyrin and three disubstituted derivatives (with O, S or Se atoms) is performed in order to obtain an accurate theoretical description of their capability as photosensitizers in photodynamic therapy (PDT). For the calculation of the V/UV spectra, we used two functionals already tested for porphyrin derivatives, B3LYP and PBE0, and two new ones recently proposed, MPWB1 K and M05, all of them with two different basis sets and two continuum solvent models. The best agreement with experimental data was obtained at the CPCM-M05/6-31 + G(d)//B3LYP/6-31 + G(d) level, at which errors lie in the range of 0.13–0.20 eV for the Q band in CH2Cl2 solution. A careful comparison between triplet and singlet geometries shows that the inner macrocycle enlarges, but planarity distortions lead to a volume contraction upon excitation to the triplet state for sapphyrin, and O and S heterosapphyrins, and to negligible volume changes for Se heterosapphyrin. Actually, the heterosapphyrins with S and Se atoms acquire a saddle shape in the triplet state. According to our results, the energy released from the triplet state for S- and Se- disubstituted sapphyrins could be adequate to generate activated oxygen both in the gas phase and in CH2Cl2 solution.