A method for obtaining electronic bands in the helical Brillouin zone based on the results of high-level quantum mechanical calculations using the CRYSTAL17 software package is considered. Using the example of a carbon nanotube of chirality (4,1), the preference of helical Brillouin zone in comparison with the translational Brillouin zone is shown. For nanohelicene, a system which is helically periodic only, bands of electronic states were obtained corresponding to the structure closest to the energy minimum. In addition, the evolution of the electronic bands of nanohelicene depending on torsion distortions is presented.