Oxygen, hydrogen, and chlorine atoms react with vibrationally excited HCN to produce CN and OH, H-2, or HCl, respectively. The experiments presented here use direct vibrational overtone excitation to prepare states of HCN having four quanta of C-H stretching excitation [(004) state] or three quanta of C=N stretching and two quanta of C-H stretching excitation [(302) state] and laser-induced fluorescence to determine the rotational and vibrational states of the CN product. We find that the reaction of HCN with O produces CN having little vibrational and rotational energy, with 85% of the CN in nu = 0, 12% in nu = 1, and 3% in nu = 2. The CN from the reaction of H with HCN is slightly more energetic, with 77% in nu = 0, 17% in nu = 1, and 6% in nu = 2. By contrast, the reaction of Cl with HCN produces CN with a considerable amount of excitation, about 30% is in nu = 1 and at least 10% is in nu = 2, depending on the initial vibrational state of the HCN reactant. The enhanced excitation of the CN product of the reaction with Cl reflects the contribution of a different mechanism. We conclude that the O-atom reaction forms CN exclusively by a direct abstraction reaction, the H-atom reaction produces CN primarily by direct reaction at the collisional energies of our experiment, and the Cl-atom reaction forms CN by the dissociation of an intermediate complex in addition to the direct abstraction reaction.