For exploring the C, D, and E states of the SO2+ ion, eight excited states of SO2+, 2(2)A(1), 3(2)A(1), 2(2)B(2), 3(2)B(2), 1(2)B(1), 2(2)B(1), 3(2)B(1), and 2(2)A(2), have been studied using the complete active-space self-consistent field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) methods in conjunction with two contracted atomic natural orbital basis sets, S[6s4p3d1f]/O[5s3p2d1f] (ANO-L) and S[4s3p2d]/O[3s2p1d] (ANO-S) (the 1(2)A(1), 1(2)B(2), and 1(2)A(2) states were previously studied and assigned to the X, A, and B states, respectively). Equilibrium geometries and the upsilon(1) and upsilon(2) vibrational frequencies for the eight excited states were predicted at the CASSCF/ANO-L level. For the eight states, the CASPT2/ANO-L adiabatic excitation energy (T-0) and vertical excitation energy (T-v) values were calculated using the CASSCF/ANO-L geometries, and the CASPT2/ ANO-L relative energy (T-v') values to X(2)A(1) were calculated at the SO2 molecular geometry. The CASPT2/ ANO-L To ordering is: 1(2)B(1), 2(2)B(1), 2(2)A(2), 2(2)A(1), 3(2)A(1), 2(2)B(2), 3(2)B(2), and 3(2)B(1) (in increasing order of energy), and five of these states have shake-up ionization character. We assign the observed C, D, and E states of SO2+ to 1(2)B(1), 2(2)A(1), and 2(2)B(2), respectively, and the three calculated states have primary ionization character at the molecular geometry. The CASPT2/ANO-L T-0 values and the CASSCF/ANO-L upsilon(1) and upsilon(2) values for 1(2)B(1) and 2(2)A(1) are in good agreement with the experimental T-0, upsilon(1), and upsilon(2) values for the C and D states, respectively. The CASPT2/ANO-L T-0 value and the CASSCF/ANO-L upsilon(1) and upsilon(2) values for 2(2)B(2) are in reasonable agreement with the experimental T-0, upsilon(1), and upsilon(2) values for the E state, respectively. For preliminarily exploring the potential energy surfaces (PESs), potential energy curves (PECs) of the eight excited states, as functions of the OSO bond angle, were calculated at the CASPT2/ANO-S level, and then in the CASSCF/ ANO-L PESs of 1(2)B(1) and 2(2)A(1) we found other minimum energy geometries which have lower CASPT2/ ANO-L energies than the "equilibrium geometries" of the respective states. However, these geometries are far away from the Franck-Condon regions for the ground-state molecule and ion. For preliminarily exploring dissociation processes of SO2+, a Jacobi coordinate system (C-s symmetry) was adopted and dissociation potential energy curves (DPECs) for the 1-6(2)A' and 1-5(2)A" states were calculated at the CASPT2/ANO-S level. The calculations indicate that the 1(2)A', 2(2)A', 3(2)A', 1(2)A", 2(2)A", and 3(2)A" DPECs converge to the first dissociation limit [SO+ ((XII)-I-2) + O ((3)Pg)] By considering the correlation relations of the C-S states with the C-2upsilon states and our assignments for the C, D, and E states, we conclude that, among the C, D, and E states, only two directly correlate to the first dissociation limit.