A master's thesis in the College of Science discussed the calculation of the electronic band structure and the optical properties of cadmium telluride (CdTe) and cadmium selenide (CdSe). The thesis presented by the student Azhar Jalal Brajas aimed to study the electronic and optical properties of cadmium telluride (CdTe) and cadmium selenide (CdSe) using the density functional theory (DFT) in the implemented CASTEP code and using the local density approximation (LDA) and the parameter gradient approximation (GGA-PBESOL). To calculate the electronic and optical properties. The thesis concludes that there is an agreement between the theoretical results of the energy gap and the practical results, as the calculated direct band gap for (CdTe) is 1.329 eV for LDA and 1.392 eV for GGA, and for (CdSe) it is 0.408 eV for LDA and 1.105 eV for GGA at a point G.