Multi-reference configuration interaction calculations are presented for excited states of the NO2+ molecular ion. Bending potential energy curves are calculated for a number of low-lying states and dissociation to [NO+O](+) is considered for linear geometries and for a bond angle of 120 degrees. The very fast dissociation of the (b) over tilde (3)A(2) state can be understood in terms of a very shallow quasi-bound minimum on the potential energy surface whereas the potential well for the (a) over tilde B-3(2) state is considerably deeper. Potential energy curves relevant to the reaction N+(P-3)+O-2(X (3)Sigma (-)(g)) are calculated. It is suggested that the reaction proceeds via a nonadiabatic transition in the entrance channel from the 2 (1)Sigma (+) surface to the 1 (1)Sigma (+) surface which correlates adiabatically with O(D-1)+NO+(X (1)Sigma (+)). The observation of O(P-3)+NO+(X (1)Sigma (+)) as a minor channel is interpreted in terms of a nonadiabatic transition, mediated by spin-orbit coupling, from the 1 (1)Sigma (+) surface to the 1 (3)Pi surface in the exit channel.