Strategies to stabilize delocalized structures in higher annulenes have been explored using density functional calculations at the B3LYP/6-31G(d) level. Symmetrically placed methylene bridges in - and annulenes favor delocalized structures (D-6h) over localized (D-3h) ones whereas - and annulenes still prefer localized structures after modification. Aromatic stabilization energy in delocalized structures reaches a constant value of 1.5 kcal/mol per pi -electron pair from annulene. Strain is higher in smaller annulenes (D-6h) and decreases as the annulenes become larger. Localized annulenes (D-3h) exhibit much smaller ring strain energy, which steeply falls down for higher annulenes. (C) 2001 Elsevier Science B.V. All rights reserved.