The rotational spectra of 3-fluoro-benzyl alcohol and of its OD isotopologue have been measured by free jet absorption millimeter wave spectroscopy. The spectrum is consistent with a gauche conformation of the oxygen atom, characterized by a OC alpha-C1C2 dihedral angle of approximately 50 degrees, and with the hydroxyl group zusammen with respect to the F atom. mu(c)-Type transitions are split into two evenly spaced component lines by approximate to 1.64 MHz, showing that the CH2OH group undergoes a tunnelling motion which connects two equivalent minima above and below the aromatic ring. The barrier to inversion has been calculated to be 155 cm(1). (C) 2010 Elsevier B.V. All rights reserved.