The photoelectrochemical (photovoltaic and photocatalytic) properties of single crystal CdS electrodes modified with polymeric films of {Ru(v-bpy)(3)](2+) (v-bpy is 4-vinyl-4-methyl-2,2-bipyridine) are presented. Such modified electrodes exhibit longer lifetimes than their native counterparts when operated in a photovoltaic cell with the free and immobilized ferro/ferri cyanide redox system. The photocatalytic behavior with I-3(-)/I- with and without sulfite solution has also been investigated.