The electronic spectrum of benzaldehyde has been studied by using multiconfigurational second-order perturbation theory through the multistate extension (MS-CASPT2). The n pi* 1(1)A " state, placed vertically at 3.71 eV, is assigned to the lowest band. The 1(1)A ' --> 2(1)A ' and 1(1)A ' --> 3(1)A ' transitions, of pi pi* nature, located at 4.33 and 4.89 eV, are responsible for the second- and third-energy bands, respectively. The most intense feature involves the 4(1)A ' and 5(1)A ' pi pi* excited states, calculated to be 5.98 and 6.23 eV above the ground state, In addition, excited states corresponding: to the low-lying Rydberg series are related to the available experimental data. Geometry optimizations for the ground state and low-lying excited states of both n pi* and pi pi* characters have been carried out at the CASSCF level. The relative ordering of the lowest n pi* and pi pi* triplet states varies depending on the geometry employed. Furthermore, the S-1(n pi*) and T-2(pi pi*) potential hypersurfaces are found to intersect upon relaxation in S-1, providing a possible explanation for the efficient singlet-triplet intersystem crossing occurring in benzaldehyde.