We have recomputed the activation barriers for the different modes of ring opening of the cyclobutene radical cation (see: Sastry, G. N.; Bally, T.; Hrouda, V.; Carsky, P. J. Am. Chem. Sec. 1998, 120, 9323) in CHCl3, a typical solvent for studies of radical cation reactions, by a polarizable continuum model. Thereby, we found a clear preference for the reaction leading directly to trans-butadiene radical cation via a cyclopropenyl-carbinyl type radical cation, in contrast to expectations of a normal "electrocyclic" pathway leading to cisbutadiene radical cation.