To examine the experimentally suggested scheme of the pathways for Cl-and H-loss dissociations of the CH3Cl+ ion in the (XE)-E-2 (1(2)A', 1(2)A"), A(2)A(1) (2(2)A'), and (BE)-E-2 (3(2)A', 2(2)A") states, the complete active space-self-consistent field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) calculations with an atomic natural orbital (ANO) basis were performed for the 1(2)A' (X(2)A'), 1(2)A", 2(2)A', and 2(2)A" states. The potential energy curves describing dissociation from the four C, states were obtained on the basis of the CASSCF partial geometry optimization calculations at fixed C-Cl or C-H distance values, followed by the CASPT2 energy calculations. The electronic states of the CH3+ and CH2Cl+ ions produced by Cl-loss and H-loss dissociation, respectively, were carefully determined. Our calculations confirm the following experimental facts: Cl-loss dissociation occurs from the 1(2)A' (X(2)A'), 1(2)A", and 2(2)A' states (all leading to CH3+ (X(1)A(1)') + Cl), and H-loss dissociation does not occur from 2(2)A'. The calculations indicate that H-loss dissociation occurs from the 1(2)A' and 1(2)A" states (leading to CH2Cl+ (X(1)A(1)) + H and CH2Cl+ (1(3)A") + H, respectively). The calculations also indicate that H-loss dissociation occurs (with a barrier) from the 2(2)A" state (leading to CH2Cl+ (1(1)A") + H), supporting the observation of direct dissociation from the B state to CH2Cl+ and that Cl-loss dissociation occurs from the 2(2)A" state (leading to CH3+ (1(3)A") + Cl), not supporting the previously proposed Cl-loss dissociation of the B state via internal conversion of B to A. The predicted appearance potential values for CH3+ (X(1)A(1)') and CH2Cl+ (X(1)A(1)) are in good agreement with the experimental values.