We present theoretical studies based on an empirical tight-binding (TB) method to provide a statistical understanding of the electronic structures of disordered III-V (InAs, InP, GaSb) and IV (Si) semiconductor quantum dots (QDs). Both the energy levels and wavefunctions of disordered QDs with different sizes, shapes, and materials are computed. A statistical model of the bandgap distributions of disordered QDs with different sizes, shapes, and materials is suggested.