The photodissociation dynamics of HF and DF, following electronic excitation, are examined using time-dependent wave packet techniques. The calculations are based on new multireference configuration interaction calculations of the potential energy curves and complete active space self-consistent field calculations of the off-diagonal spin–orbit coupling matrix elements. The calculated branching fraction for the formation of excited state fluorine, following excitation from the ground vibrational state of HF, agrees well with the value of measured experimentally at 121.6 nm by Zhang et al. [J. Chem. Phys. 104, 7027 (1996)]. Predictions are made for the excited spin–orbit state branching fraction for both HF and DF over a wide range of photon excitation energies. The results for HF and DF are discussed in context with the corresponding results for the photodissociationof HCl and DCl.