We have investigated the photodissociation of chlorobenzene and 3-chloropyridine adsorbed on smooth and rough Ag surfaces. Photolysis of adsorbed chlorobenzene and 3-chloropyridine with UV radiation results in C-Cl bond dissociation. Biphenyl and bipyridyl desorb from the surface near 400 K, and AgCl desorbs near 800 K in postirradiation temperature-programmed desorption. Compared to a smooth surface, there is a red shift in the photodissociation threshold for both molecules when adsorbed on a rough surface. Possible mechanisms for the red shift are discussed. This study demonstrates the importance of substrate morphology on surface photochemistry.