This study compared the textural characterization of montmorillonite pillared with mixed aluminum cerium pillars with that of a sample pillared only with aluminum. In addition to the microporosity due to the aluminum pillars, the AlCe-pillared sample exhibited a new porous system, with a pore size at the limit between microporosity and mesoporosity. The pore size distribution determined by the density functional theory and Horvarth-Kawazoe methods allowed estimation of pore volume and indicated two different types of pore in the AlCe-pillared sample. The two types of pore were also observed on t-plot analysis. The presence of larger pores in the AlCe-pillared sample is due to the inorganic polyoxycations intercalated between the clay layers. These polyoxycations are larger than the Keggin ion intercalated in the sample pillared with aluminum alone.