The microporosity of aluminium pillared montmorillonite has been investigated by nitrogen adsorption, X-ray diffraction and electron microscopy. Control of the preparation conditions allowed the synthesis of solids with two types of micropores. Comparison of XRD measurements and Horvath-Kawazoe analysis of very low-pressure nitrogen adsorption have shown a new promising way to increase the micropore characterization. Disagreement between data from different techniques could be related to the different experimental conditions during measurements and to uncertain values of the interaction parameter in the Horvath-Kawazoe analysis.