We have investigated the structural, electronic, and optical properties of Zn1-xCaxSe ternary alloys using first principles calculations within the plane-wave pseudopotential method. Some basic physical properties, such as lattice constant, bulk modulus, electronic band structures, and optical properties (dielectric functions, refractive index, and energy loss function) were calculated. In addition, the effects of composition x on bulk modulus, band gap, refractive index and dielectric function were calculated. Our results agree well with the available data in the literature. (C) 2010 Elsevier Ltd. All rights reserved.