Two alternative approaches-vertical and adiabatic-are used to estimate global and local electrophilicity (omega and omega(+)(k)) indexes for a series of aryl cations in both the ground and first excited electronic states using the well-known Parr scheme. The energy parameters used in these methods are obtained by the B3LYP/6-311++G(2d,2p) calculations of the aryl cations and of their oxidized and reduced forms in acetonitrile medium. The ground state omega values are lower than those for the excited state, which is in accord with the maximum hardness principle. Analysis of the omega indexes calculated with more reliable adiabatic approach reveals a dependence of the ground and first excited state omega indexes on the singlet-triplet energy gap of the aryl cations. A plot of the above dependence has a hyperbola-like shape; thus, the maximum (ground state) and minimum (first excited state) omega indexes correspond to the aryl cation, for which the singlet-triplet splitting is close to zero. Moreover, the omega(+)(k) index distribution at the ipso-carbon atoms does not obey the maximum hardness principle, since it depends on spin multiplicity, not on the electronic state spatial type. For many singlet ground state aryl cations, the omega(+)(k) indexes at the ipso-carbon atom are lower when calculated in the excited triplet state; that is due to a strong omega delocalization onto two electrophilic centers. This explains a higher chemoselectivity of the triplet aryl cations in reactions with the pi-nucleophiles compared to the corresponding singlet arylium species. Applicability of the adiabatic approach for calculation of the omega and omega(+)(k) indexes is supported by the experimental data on the nucleophile-independent parameter E for the singlet and triplet state of the p-Me2NC6H4+ cation.