The effect of various amorphous aluminosilicates on the composition of cracking products of Karmalskoe heavy oil (Republic of Tatarstan) in an autoclave reactor has been studied. It has been shown that additives of 0.5% aluminosilicates with a pore size of 70 angstrom and 1.0 wt % Al-Si with a pore size of 50 angstrom lead to an increase in the degradation of macromolecular components by 13-14% and the yield of fractions boiling below 360 degrees C by more than 20 wt %. It has been revealed that the oils are enriched in saturated and monoaromatic hydrocarbons. It has been found that the addition of an amorphous aluminosilicate with a pore size of 50 angstrom leads to the formation of asphaltenes with a coke-like structure and a low H/C atomic ratio of 0.75 and to complete catalyst coking. The use of an amorphous aluminosilicate with a pore size of 70 angstrom leads to the formation of asphaltenes with a lower molecular weight and an H/C atomic ratio of 0.96; in this case, the catalyst is less susceptible to the deposition of condensation products.