CuInSe2 has been grown on ZnSe by LPE from the Bi solution. The value of lattice mismatch is 2.06%. The reflection electron diffraction pattern showed an epitaxial growth. Optimum growth condition was the following: maximum temperature of 600°C, cooling rate of 0.5°C/min, thickness of the over-growth layer of 6 µm and thickness of mixed crystal layer of 4.5 µm. The flatness of overgrowth surface was dependent on the substrate orientation and the quality was in order of (111)Se, (100), (111)zn and (110). Hall measurements on over-growth layer were carried out after the heat-treatment in Se and Zn atmosphere for 10 minutes at 600°C. The p·CuInSe2–n·ZnSe and n·CuInSe2–n·ZnSe heterodiodes were measured for their I–V, C–V characteristics and photoresponse. Especially, the n-n heterodiode showed a high photosensitivity.