In this paper, an ab initio molecular orbital study of carbazole model compounds has been performed. Carbazoles (KPA) are very useful organic electronic materials for they are both semi-conducting (p-type) and light-emitting (in the blue and UV range). By means of self-consistent Hartree–Fock method and density functional theory, the absorption and light-emitting properties of carbazole model compounds are investigated theoretically. The optimized structures, frontier orbitals, absorption and emission energy spectra are examined in order to give a better understanding of how polar side-groups affect the electronic properties of the compounds.