Photoelectrodes made of nanocrystalline titanium dioxide modified with hexacyanoferrate anions exhibit unique photoelectrochemical properties: photocurrent direction can be switched from anodic to cathodic and vice versa upon changes in photoelectrode potential and incident light wavelength. This effect, called photoelectrochemical photocurrent switching (PEPS effect), can serve as a basis for construction of chemical logic gates with optical inputs and electric output. At certain potentials anodic photocurrent generated upon UV irradiation has the same intensity as the cathodic photocurrent generated upon visible irradiation. Under these conditions simultaneous irradiation with UV and visible light results in compensation of anodic and cathodic photocurrents and zero net photocurrent is observed. This process can be used for construction of unique light-driven chemical logic gates. Due to reversible electrochemical process leading to oxidation or reduction of the surface species the device can be programmed to perform XOR, OR or YES logic operations.