The electronic structure, molecular structure, and electronic spectra of lanthanide(III) mono- and bisporphyrin complexes are investigated using a DFT/TDDFT method. These complexes include YbP( acac), YbP2, [ YbP2](+), YbHP2, and [ YbP2](-) ( where P) porphine and acac) acetylacetonate). To shed some light on the origin of the out-of-plane displacement of Yb in YbP( acac), unligated model systems, namely, planar D-4h and distorted C-4v YbP, were calculated. For comparison, the calculations were also extended to include the (CeP2)-P-IV and [ (CeP2)-P-IV](+) systems. Even without an axial ligand, the lanthanide atom lies considerably above the porphyrin plane; the distortion of the YbP molecular structure from a planar D-4h to the nonplanar C-4v symmetry leads to a considerable energy lowering. The axial ligand makes the metal out-of-plane displacement even larger, and it also changes the redox properties of the lanthanide monoporphyrin. The ground-state configurations of YbP2 and YbHP2 were determined by considering several possible low-lying states. YbP2 is confirmed to be a single-hole radical. The special redox properties of the bisporphyrin complexes can well be accounted for by the calculated ionization potentials and electron affinities. The TDDFT results provide a clear description of the UV-vis and near-IR absorption spectra of the various lanthanide porphyrins.