Aromaticity has always been a fundamental concept in the study of various phenomena in chemistry. It has long been known as the only interaction between ? orbitals, however, today it is also known to be the interaction between ?, ?, and ? electrons, In fact, dual aromaticity is the result of the simultaneous existence of two types of cyclic delocalization of electrons (? and ?) leading to more stability in the molecule. Since this concept does not have a precise definition, different criteria are used to examine it quantitatively and qualitatively. In this thesis, the dual aromaticity in different structures with the general formula C_6 X_6 in which X is H, F, Cl, S^- , SH, S^- Li^+ or SCH_3 have been studied. The Indexes such as PDI، HOMA، NICS(0), NICS(1) and also Localized-Delocalized Matrix (LDM)، have been used to study the dual aromaticity in these compounds. The results show that PDI and HOMA indexes, which consider only the central ring, are not a suitable criterion for evaluating the aromaticity of these compounds. On the other hand, the LDM matrix, which considers both the inner and outer rings, provides a description that is more consistent with the NICS, especially NICS(0) results. The IQA calculations also reveal the stability arises from the electron delocalization in the aromatic compound