A harmonic force field for difluorodioxirane was derived from fundamental wavenumbers, isotopic shifts, centrifugal distortion constants, and inertial defect differences. The following geometric structure was determined by a joint analysis of gas electron diffraction intensities and rotational constants of the parent species (r(z) values with 1 sigma uncertainties) : O-O = 1.578(1), C-O = 1.348(8), C-F = 1.317(6) Angstrom, angle FCF = 108.8(7)degrees. The extremely long O-O bond correlates with the small force constant of 2.94 x 10(2) N m(-1).