A theoretical analysis on planar and puckered-ring conformations of cyclopentadiene, 2,3-dihydrofuran, and 1,3-dioxole is carried out to test the conclusion of Laane and co-workers (J. Am. Chem. Soc. 1993, 115, 12132) that the unexpected nonplanarity of 1,3-dioxole must be attributed to the anomeric effect. MP4/6-31G**/IMP2/6-31G** calculations and NBO analysis show that delocalization involving the oxygen lone pairs and the C-O antibonding orbital, commonly associated with the anomeric effect, plays a decisive role in explaining the above-mentioned experimental fact. A careful analysis of the dipole-dipole interaction energy indicates that, in the present case, the electrostatic theory does not help to rationalize the experimentally observed puckered-ring conformation of 1,3-dioxole.