Whereas the radical cation of bicyclopropylidene (1) in a CF3CCl3 matrix rearranges to that of tetramethyleneethane (2) already at 77 K, it persists in CFCl3 and CF2ClCFCl2 matrices up to ca. 100 K, giving rise to a well-defined ESR spectrum. On going from 1 to 1(.+), the set of eight equivalent beta-protons splits into two sets of four, as the two protons in each CH2 group have greatly differing coupling constants, 2.24 and 0.27 mT. This striking inequivalence is due to considerable changes in geometry upon ionization of 1, such as a twist about the central C(1)-C(1’) bond and some unusual features of the electronic structure of 1(.+). Above 100 K, the spectrum of a secondary paramagnetic species appears which in the CFCl3 matrix is also 2(.+). In the CF2ClCFCl2 matrix, on the other hand, an allyl-type radical 4(.) is formed by the loss of a proton from 1(.+), without opening of the three-membered rings.