Various types of 2,3- and 1,2-benzo-substituted zinc-phthalocyanines were prepared to investigate the influence of the substitutions on the electronic states of phthalocyanine (Pc) compounds. The experimental data showed that these compounds can be categorized by their spectral patterns. A simple perturbation method based on the group theory (symmetry-adapted perturbation method) is presented to analyse the spectroscopic changes of Pc compounds caused by the substitutions. This method was tested against the experimental data and gave good agreement.