Multireference configuration interaction calculations with the cc-pVQZ basis set are reported for the potential-energy surfaces of the (X) over tilde B-2(1), (A) over tilde (2)A(1), (B) over tilde B-2(2), 1 (4)A(2), and 1 B-4(1) states of H2S+. Seams of intersection between the states have been characterized and the conical intersection between the (A) over tilde (2)A(1) and (B) over tilde B-2(2) states has been located. Optimized geometries and vertical and adiabatic ionization energies are in good agreement with the available experimental data. The (X) over tilde B-2(1) state is strongly bound with an equilibrium geometry very similar to that of ground-state H2S. The equilibrium bond angle for the (A) over tilde (2)A(1) state is 126.4degrees. The dissociation of this state to S+(S-4)+H-2 is interpreted in terms of an initial increase in bond angle on formation and a transition to the (X) over tilde B-2(1) surface at linearity. As the bond angle decreases the intersection with the 1 (4)A(2) state is reached and a nonadiabatic transition to this state results in dissociation. It is suggested that the dissociation of the (B) over tilde B-2(2) state to SH+((3)Sigma(-))+H occurs via asymmetric stretching followed by a nonadiabatic transition to the dissociative 1 (4)A" surface. (C) 2003 American Institute of Physics.