The pore architecture of alkaline treated HMCM-22 zeolite was investigated by Xe-129 NMR spectroscopy. The spectra show that additional porosities have been formed after the alkaline treatment. Up to a treatment with 0.20 M NaOH new micropores are formed which gradually grow in size to the mesoporous range at higher alkaline treatment conditions. Furthermore, interconnections between the two independent channel systems are formed, leading to an increase in the porosity and a further evolution of the porosity towards the mesoporous range. The results are in accordance with earlier characterization and catalytic results and conclusions drawn in our previous study. (C) 2011 Elsevier B.V. All rights reserved.