We report quantum mechanical calculations of excitation functions (relative reaction cross sections) for the F+HD reaction. We include three potential energy surfaces and an accurate treatment of all couplings (non-adiabatic, spin-orbit, and Coriolis). Comparison with experimental results [Dong, Lee, and Liu, J. Chem. Phys., 113, 3633 (2000)] show excellent agreement for the DF product channel and an improved but not perfect agreement for the HF product channel. In the former case, when weighted by the (16%) fractional population of the spin-orbit excited state (F*) in the beam, the overall reactivity of the F* is small (similar to5%). For the HF product channel and with the same (16%) fractional weight, F* reactivity makes a contribution of similar to12% in the high-energy tail of the resonance peak. As a result, averaging over the population of F spin-orbit states in the beam changes the shape of the resonance. The greater the fraction of F* in the beam, the less pronounced will be the resonance modulation of the reaction excitation function. (C) 2004 American Institute of Physics.