The competitive photodissociation of bromoacetyl chloride has been investigated by means of ab initio methods. Quantum dynamics in full dimensionality is prohibitive for such a system and therefore a reduced dimensionality method based on constrained Hamiltonians has been used. A one-dimensional (1-D) non-adiabatic wave packet treatment in the C-S optimized geometry (trans Cl and Br) on the first excited states leads to encouraging results when compared to experimental data. The slow relaxation of the torsion angle is assessed by a 2-D dynamics in the subspace including the C=O bond length. (C) 2003 Elsevier Science B.V. All rights reserved.