Crystallisation of mesoporous molecular sieves of SBA-3 structure carried out from the gel containing heteropoly acids (HPA) (pH < 2) resulted in the formation of new mixed mesostructure, which included the Keggin units in mesoporous material walls. Correct mesostructure was formed up to 20 wt.% of HPW in the system. Template removal by means of calcination preserved mesoporous structure, while washing of calcined samples with polar solvents resulted in the Keggin unit removal from the walls and in consequence in mesostructure collapse. (C) 2003 Elsevier B.V. All rights reserved.