The millimeterwave spectra of F 2 10 BOH and F 2 11 BOH (difluorohydroxyborane) have been measured in their ground vibrational state. Accurate rotational and centrifugal distortion constants have been determined. The equilibrium geometry and anharmonic force fields have been calculated at the CCSD(T) level of theory. The ab initio centrifugal distortion constants and rotation–vibration interaction constants are compared to the experimental values. Some discrepancies are found and discussed. Particularly, it is explained why the semi-experimental structure is not reliable. The best equilibrium structure is: r e (BF cis )=132.29pm, r e (BF trans )=131.29pm, r e (BO)=134.48pm, r e (OH)=95.74pm, ∠ e (FBF)=118.36°, ∠ e (F cis BO)=122.25°, and ∠ e (BOH)=113.14°.