Methanol adsorption and desorption experiments were performed on acidic zeolites applying a new in situ MAS NMR technique. H-1 MAS NMR spectra of dehydrated zeolites were recorded during injection of nitrogen gas loaded with methanol into the MAS rotor. The spectra indicated that in zeolite HBeta also silanol groups are involved in the adsorption of methanol which is in contrast to the behaviour of SiOH groups in zeolites HZSM-5 and HY. The desorption experiments show that about 70% of the methanol molecules contributing to adsorbate complexes in zeolite HBeta are weakly hydrogen-bonded at silanol groups.