Time-dependent B3LYP/6-31G* calculations have been performed at the optimized G(2) or C-2v geometries of several substituted semibullvaienes (1(deloc)) and barbaralanes (2(deloc)), to compare the computed vertical electronic excitation energies with the temperature-dependent, long-wavelength absorptions that have been observed in the UV/vis spectra of some of these compounds by Quasi and co-workers. The excellent agreement between the calculated vertical excitation energies and the observed values of amp provides strong support for the identification of the bishomoaromatic species 1(deloc) and 2(deloc) as the source of these absorptions. Furthermore, the CN stretching frequencies, computed for the C-2 geometry of 1,5-dimethyl-2,6-dicyano-4,8-diphenylsemibullvalene (1f(deloc)), fit the low-frequency absorptions seen in the IR spectrum of 1f, thus furnishing independent evidence that bishomoaromatic geometries of semibullvalenes have, in fact, been observed spectroscopically. B3LYP/6-31G* calculations predict that 2,6-dicyano-4,8-diphenylsemibullvalene 1c has a C-2 equilibrium geometry (1c(deloc)) and that the long-wavelength UV/vis absorption (lambda(max) = 585 nm) and CN stretching frequencies (2192 and 2194 cm(-1)) computed for 1c(deloc) should serve to identify this bishomoaromatic semibullvalene when it is synthesized.