Ab initio MO calculations at the SCF level using 6–31 G* basis sets show that only 2.1 kcal mol–1 more energy is needed to form perhydrotriquinacenyl cation 1 from the corresponding hydrocarbon than to form the tert-butyl cation from 2-methylpropane; such a stabilisation energy is comparable to those computed for 1-noradamantyl cation 2, 3-noradamantyl cation 3, and bicyclo[3.2.1]octan-1-yl cation 4, which are shown to be stabilized efficiently by C–C hyperconjugation.