The photodissociation dynamics of HF and DF, following A ¹Π←X ¹Σ⁺ 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,  ,F*(²P_1/2), following excitation from the ground vibrational state (v=0) of HF, agrees well with the value of 0.41±0.08 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.