The SAC (symmetry adapted cluster)/SAC-CI method was used to calculate the ground, excited, and ionized states of carboxy P450 model complexes. The excited and ionized states were calculated up to 5.9 and 3.4 eV, respectively. Our initial calculations were with the D-4h-skeleton model structure. The Q-band was well described, but the BI band (lower of the split Soret bands) was higher than the experimental value by 0.7 eV and the BIT band (higher of the split Soret bands) did not appear. Next, we used the distorted X-ray crystallographic structure with side chains on porphyrin. The calculated results reproduced not only the Q-band but also both the BI and BIT bands in reasonable agreement with experimental findings with regard to both absorption positions and intensities, thus demonstrating the importance of using the actual molecular geometry. In particular, the BIT band is attributed to excitation from the pi bond of the porphyrin side chain. We examined the effect of proteins on the spectrum by using the point charge model for environmental proteins. We then examined the effect of the double bond of the porphyrin side chain by saturating it with the thiohydrate bond and clarified that the experimental geometry is important for reproducing the BI band and that the double bond of the porphyrin side chain is important for reproducing the BIT band. We also performed calculations for ionized states as a model of compound I (oxo-Fe(IV) porphyrin pi -cation radical complex) of P450s. The lowest energy state was the porphyrin pi cation radical with A(2u)-like symmetry.