A mixture of n-paraffins as well as a hydrotreated gasoil were hydrocracked over a Pt/ZSM-22 and a Pt/USY zeolite catalyst in a three phase reactor with complete internal mixing operated under industrially relevant conditions. The distribution of the isomerization products obtained from the n-paraffin mixture and the hydrotreated gasoil on Pt/ZSM-22 shows that pore-mouth and key-lock catalysis are operative, although the selective formation of branching at the end of the carbon chain is less pronounced. Ethylbranching is suppressed in liquid as well as vapor phase conditions. The cracked products obtained on Pt/ZSM-22 for both feedstocks contain a high amount of linear paraffins in comparison to the amount observed for hydrocracking on Pt/USY. This indicates that similar to vapor phase operations, the scission of the bond in the beta position of the positively charged secondary carbon atom towards a new secondary carbenium ion (s,s beta-scission) is also the dominant cracking mechanism for operations in liquid phase. The differences between vapor and liquid phase operations of Pt/ZSM-22 are attributed to differences in the adsorption modes of the molecules. (C) 2000 Elsevier Science B.V. All rights reserved.