We investigated the photodissociation of HNO3 within the first (300 nm) and the third (200 nm) absorption band. The relevant S-1 and S-3 potential energy surfaces were calculated by taking into account the N-O single bond and N=O 'double' bond distances. The striking feature of the dynamical analysis is a bifurcation of the wave packet on the S-3 surface which explains the branching into the two reaction pathways with the products OH + NO2 and O + HONO found in experiments. Dissociation on the S-1 surface is predicted to proceed along a single channel leading to OH + NO2, both in their electronic ground states. (C) 2010 Elsevier B.V. All rights reserved.