The catalytic properties of extra-large pore aluminosilicate MCM-41, silicon containing VPI-5 and aluminium containing ETS-10 were investigated by MAT (Micro Activity Test) using n-hexadecane and 1,3,5-triisopropylbenzene as the model feeds and were then compared with the results obtained from Y zeolite in the I-I-form and a commercial FCC (Fluid Catalytic Cracking) catalyst. It could be demonstrated that not only the acidic properties of the investigated materials, but also the accessibility to the internal active sites of the investigated materials have a significant influence on activity and selectivity. It can be assumed that, by optimising structural and chemical properties, the mesoparously organised MCM-41 and related materials are suitable as active components in cracking catalysts for ＇＇deeper＇＇ cracking of high boiling hydrocarbons.