A combined experimental and theoretical study of electronic and structural properties of radical cations of phenylene vinylene (PV) oligomers was described. PV cations in solution were produced using pulse radiolysis. Thus, the cation optical absorption spectra were measured for a variety of PV's differing in chain length and substitution pattern. It was found that the cation optical absorption spectrum depends strongly on the pattern of substitution. This indicates that substituents influence the degree of delocalization considerably.