Structural, electronic and optical properties of Ca xCd 1-xO (0 ≤ x ≤ 1) in rocksalt phase are calculated using full potential linearized augmented plane wave (FP-LAPW) method. The results show that the bandgap as well as structural and optical properties of the compound varies with the Ca concentration. The substitution of Cd by Ca, larger than 25%, transforms the ternary oxide from semi-metallic into indirect bandgap semiconductor. The bandgap increases with the increase in calcium while the bulk moduli decreases. The density of states shows that maximum contribution to the valence and conduction bands are due to the Cd-4d, O-2p, Ca-3p and Ca-3d states. Optical properties in the incident photon energy range 0-30 eV reveal that the real part of the complex dielectric constant decreases with the increase in the Ca concentration. © 2012 Elsevier B.V. All rights reserved.