Abstract The torsional and rotation–torsion spectra of the doubly deuterated species of methanol CD2HOH have been analyzed using submillimeter wave, terahertz, and far infrared spectra. 101 torsional subbands, with subband centers ranging from 2.3 to 626 cm−1, were assigned. Analysis of these yielded kinetic energy and hindering potential parameters of the torsional Hamiltonian describing the large amplitude internal rotation of the CD2H methyl group with respect to the hydroxyl group. 3271 rotation and rotation–torsion transitions, involving the 24 torsional levels up to e 1 with 3 ⩽ K ⩽ 10 , were assigned and fitted approximating the rotational energy of each torsional level with a Taylor-type expansion in J ( J + 1 ) . The rotational structure of 48 torsional subbands involving torsional levels higher than e 1 has also been analyzed. In most cases, only the Q branch could be observed and assigned.