The conformational analysis of substituted γ-lactones with vicinal hydrogen atoms is carried out by the MM2/3JHH tandem. The agreement between experimentally available and calculated data is globally correct (rms = 1.16 Hz). A general preference for a hydroxyl group to occupy the equatorial position if it is on C-2 or the axial position if it is on C-3 or C-4 is observed as a consequence of the presence of H bond or of the gauche effect, respectively. © 1993, American Chemical Society. All rights reserved.