A series of carbazole derivatives have been studied by means of ab initio density functional theory. The molecular structure of these compounds has been obtained by means of geometry optimization and characterized as potential energy surface minima. The analysis of the frontier orbitals together with the study of aromaticity permits one to make quantitative predictions about the reactivity of these molecules. This could be used to predict the influence of substituents on the chemical reactivity of carbazole-like moieties in asphaltenes.