A theoretical approach to the interpretation of UV/VIS spectra of radical cations is made. LND O/S PERTCI calculations including all singles and doubles with respect to the ion ground and excited state main configurations are made. Evaluations of the oscillator strengths are carried out using the full ground and ion states Cl vectors. The method is applied to [r/w«-butadiene]+, [all-taflj-hexatriene]+, [all-/ra«5-octatetraene]+, [m -butadiene]+, [all-m-hexatriene]+, [transstilbene]+, [biphenyl]+, [diphenylacetylene]+, [benzocyclobutene]+, and [o-xylylene]+. Calculated electronic excitation spectra for these systems are presented. They are compared with the UV/VIS spectra in low temperature matrices. It is shown, that LND O/S PERTCI results can be of help in the interpetation of UV/VIS spectra of cations and thus in the difficult task of identify ing such systems or cationic reaction products of cations.