Structural and textural characteristics as well as coordination states of aluminium and some catalytic properties are studied for highly-ordered (with very narrow XRD reflections) aluminosilicate mesoporous mesophase materials ((Si,Al)-MMM) prepared with different aluminium concentrations by hydrothermal synthesis in the presence of C16H33N(CH3)(3)Br. As shown, all physico-chemical parameters measured for these systems including their structural hydrostability are strongly influenced by the aluminium content. Based on analysis of the results obtained, a description of probable transformations during formation of mesoporosity in the C16-(Si,Al)-MMM is considered.