Combined micro- and mesoporous ZSM-5 zeolites with different mesopore sizes have been comparatively investigated using mercury-intrusion porosimetry (MIP) and N₂ gas adsorption. N₂ adsorption and MIP complement each other and a fairly good correlation has been obtained for the mesopore sizes and volumes derived from both techniques, confirming an adequate accessibility of the newly created mesoporosity. Elastic compression of the mesoporous zeolites during the mercury-intrusion experiments can account for the somewhat smaller average mesopore size and mesopore volume as derived from this technique. An excellent reproducibility of multiple mercury-intrusion cycles proves the mechanical stability of the hierarchical porous zeolites. Besides, MIP provides supplementary information on the presence of macropores.