Absorption edge, photoresponse, and reflectance measurements have been carried out on ZnIn₂Se₄ crystals grown by means of chemical transport reactions. Indirect and direct energy gaps were determined as E _gi=1.74 eV and E _gd=1.92 eV at LNT. Reflectance measurements have been done in the 1.5–25 eV energy range. The Kramers-Kronig analysis has been performed and optical constants of studied semiconductor have been claculated. Reflectance data (R) and calculated imaginary part (ε ₂) of dielectric function allowed to make some conclusions about interband transitions. Singularities in R, ε ₂ and valence electron concentration per atom (n_eff) were basis for conclusion that d band–conduction band transitions at energy about 12.5 eV have been observed.