A study has been carried out on the use of hybrid catalysts (physical mixture of a commercial catalyst for residue cracking with others prepared based. oil HZSM-5 zeolites) in the cracking or it mixture made up of atmospheric distillation residue with vacuum gas oil (VGO), with the latter being the standard feed ill FCC (fluidized catalytic cracking) units. The cracking has been carried out in the 525-575 degrees C range, using catalysts subjected to a severe steaming treatment in a riser simulator operating at laboratory scale under similar conditions to those of a FCC factor. The results show the relevant role of HZSM-5 zeolite on product distribution. Significant findings are the lower overcracking of LPG and gasoline fractions and the lower coke yield., which are due to the attenuation of the reactions attributable to the acid matrix of the base catalyst, The addition of HZSM-5 zeolite is also efficient for increasing the content of C-3 and C-4 olofins in the LPG and C-5 and C-6 olefins (especially i-olefins) in the gasoline and for decreasing the content of C-6-C-8 aromatics.