The forbidden S1 <-- S0 transition of acetone has been investigated by laser-induced fluorescence measurements with a resolution of 270 MHz. The rotational structure demonstrates, that (i) one deals with a-type transitions and (ii) there is a strong coupling between the torsional motion of the two CH3 groups and the tunneling, out-of-plane wagging motion (nu(23)) of acetone. The interpretation of torsion-vibrational combination bands is less conclusive and thus the discussion still has a preliminary character.