We report energy bands, density of states and optical properties of CuGaS2 and CuInS2 chalcopyrites. The electronic structure has been computed using linear combination of atomic orbitals (LCAO) scheme within density functional theory (DFT) and full-potential linearised augmented plane wave method. The energy bands, density of states, components of dielectric tensors and absorption coefficients are compared with the available data. It is seen that the present LCAO DFT calculations reproduce the electronic properties of both the chalcopyrites in a reasonable way. The optical properties show more absorption of solar radiations for CuGaS2 chalcopyrite, depicting its more usefulness in the solar cells. (C) 2010 Elsevier Ltd. All rights reserved.