Four semiempirical methods (AM1, MNDO, PM3, and MIND0/3) are used to calculate the deformation angles of [n]paracyclophanes and their Dewar benzene isomers for n = 3 . . . 10. The results obtained by all these methods are in good agreement with data from X-ray studies. We have determined the strain energies that, in both series of compounds, are due to two components: (1) the strain energy of deformation of the cycle (aromatic or Dewar benzene skeletons) and ( 2) the strain energy of the oligomethylene chain. In (61paracyclophane, the strain energy [SEring(MNDO) = 32.9 kcal/mol] almost compensates the resonance energy (Eresonance = 36 kcal/mol) so that its chemical properties are closer to alkenes than to benzenic compounds. To better reproduce the enthalpy of the valence isomerization [n]Dewar benzene + [nlparacyclophane, which is poorly calculated with these methods, a correction is proposed and the reaction enthalpy of [6]paracyclophane is estimated to be about AH, = 15 +-15 kcal/mol. It is found that MNDO and MIND0/3 need the smallest corrections, but MNDO leads to better geometries than MIND0/3. In conclusion, MNDO seems to be the best technique for further studies of these compounds.