The structures of phenylcyclopropane (1(+.)) and cumene (2(+.)) cation radicals were calculated using both CASSCF and B3LYP computational methods. Both methods predict that 1(+.) adopts a delocalized, bisected structure and that the barrier to phenyl group rotation is substantial (11-14 kcal/mol). In contrast, the spin and charge in 2(+.) is largely localized in the phenyl ring and there is no strongly preferred ground state conformation. The CASPT2 method was used to predict the electronic spectra of 1(+.) and 2(+.) The large differences in the spectra of 1(+.) and 2(+.) can be traced to significant sigma-pi interaction in 1(+.) The results are rationalized in terms of a simple valence bond configuration mixing model. In general, the calculated transition energies were in good accord with the experimental values; however, the relative UV-vis peak intensities for 1(+.) were not well reproduced if a static structure was assumed. Better agreement was obtained by taking into account libration of the phenyl group in 1(+.).