The excitation energies of the α-, β-, and p-bands of benzo-annelated polyacenes were estimated by the Pariser–Parr–Pople (PPP) molecular orbital calculation method using a novel concept for evaluating the two-centre electron repulsion integral, new-γA, in which the spectrochemical atomic softness (SCAS) parameter krA was taken into account. The value of krA was determined using the concept of the spectroactive portion (SP) and allotted to each carbon atom. The calculated results using new-γA were excellent for the simultaneous calculations of the p-, α- and β-bands of benzo-annelated polyacenes and were better than those obtained from the conventional N·M-γ or the usual new-γ. The C–C bond lengths calculated using new-γA reproduced quantitatively the observed values.