The rotational spectrum of the difluoromethane-argon van der Waals complex has been investigated by free-jet absorption millimeter-wave spectroscopy. More than 60 mu(c)-type transitions have been measured. All of them are split into two component lines due to the 'ring-puckering' of the H2C [GRAPHICS] r 'four-membered ring' and the corresponding vibrational splitting is 193.51(7) MHz. The barrier to 'ring-puckering' has been calculated to be 100(4) cm(-1). From centrifugal distortion effects the dissociation energy of the complex has been estimated to be similar to 1.5 kJ mol(-1).