Ab initio calculations at the CI (singles) level of theory were carried out for the ground state and the singlet and triplet excited states of substituted free-base porphyrins. The results predict a substantial red-shift in the long-wavelength electronic spectra of compounds due to the push-pull substitution at the pi-system of the porphyrin ring or due to the substitution by a nitro-group. The compounds and their derivatives may be good candidates for deep-penetrating photodynamic therapeutic agents.