The structures of 4,4-dibenzyloxetan-2-one, C17H16O2, (1), and 4,4-dibenzyl-3,3-difluorooxetan-2-one, C17H14O2F2, (2), were determined in order to relate their structures to differences in their reactivities toward nucleophiles and thermal decarboxylation. The lactone rings in the two compounds are different, with the former exhibiting a planar ring, while the latter has a bent ring and an average endocyclic torsion angle of 6.8 (2)°. Bond distances of the CO2 fragment are shorter in compound (2) than in their counterparts in (1).