Photosensitive structures based on single crystals of the ZnIn2S4 ternary compound were fabricated and studied for the first time. The optoelectronic properties of this compound and corresponding structures were analyzed using the results of measurements of the optical-absorption spectra of ZnIn2S4 crystals, steady-state current-voltage characteristics, and photosensitivity of the structures at T=300 K. It is concluded that surface-barrier structures and heterojunctions based on ZnIn2S4 can be used as wide-band photodetectors of natural optical radiation.