A recent paper by Bulsara, Lowen, and Rees [Phys. Rev. E 49, 4989 (1994)] presents a perturbation analysis of coherent stochastic resonance in a half-space in the presence of a field. We believe that the analysis there was flawed due to an improper use of the method of images and that a correct version of a perturbation analysis can be given by using a transformation of the underlying equations. The result still exhibits stochastic resonance.