The use of hierarchical zeolites, having a secondary porosity in addition to the zeolitic micropores, leads to an enhanced production of light olefins at the expense of aromatic hydrocarbons. A reaction scheme has been proposed in which light olefin sare formed by successive end chain cracking reactions of heavier aliphatic hydrocarbons. Oligomerization, cyclization and aromatization reactions of light olefins are proposed to account for the formation of naphthenic and aromatic hydrocarbons. According to this scheme, light olefins are primary cracking products. The shorter diffusion path existing in hierarchical ZSM-5 limits the light olefin conversion through secondary reactions, explaining the observed increase of their concentration in the gaseous stream. A common general trend for all the purely acidic catalysts along the time on stream is observed, consisting on the progressive increase in theamount of aliphatic hydrocarbons at the expense of the rest of the hydrocarbon fractions. These changes are due to the coke deposition over the catalysts, that causes deactivation of the cracking reactions of heavy hydrocarbons.