We present results of a theoretical calculation of the electronic structure of the two polar ZnSe/GaAs(100) interfaces. The bulk electronic structure is described by the nearest neighbor tight binding formalism. Using the scattering theoretical method, we have obtained wave vector-resolved interface layer densities of states and the interface band structure. For both Se/Ga and As/Zn interfaces, there exist no interface states in the fundamental gap, but there are three interface bands and four semi-resonance bands in the valence-band region. Finally, we study the nature and origins of these bands by analysing orbital-resolved layer densities of states.