The free-jet millimeter-wave absorption spectra of four isotopomers of difluoromethane(...)krypton have been assigned. The krypton is in the HCH plane of difluoromethane, 3.616 (3) &ANGS; from from its center of mass, and forms an angle of 64° (2) with the FCF plane. Ab initio and distributed polarizability model calculations confirm the observed conformation. The measured transitions are split into two component lines due to the tunnelling between two equivalent positions, with Kr above or below the FCF plane. The vibrational splitting, 79.19 (4) MHz, has been used to estimate the inversion barrier (1.23 (5) kJ mol(-1)), while an estimate of the dissociation energy (1.9 kJ mol(-1)) has been deduced from centrifugal distortion effects. © 2005 Elsevier B.V. All rights reserved.