The invention is directed to a method for modifying a microporous metalloaluminophosphate molecular sieve, the method comprising the steps of a) introducing a compound containing at least one M-X group within the cages of said microporous molecular sieve; and b) reacting said compound containing at least one M-X group with the acid groups located in the cages of the molecular sieve, wherein the compound containing at least one M-X group is selected from the group consisting of compounds of formula MX₃, compounds of formula M₂X₆, and mixtures thereof, M being a metal belonging to Group 13 of the Periodic Table, and each X independently being a hydrogen or halogen atom. Preferably, X is a hydrogen atom. The present invention also relates to modified metalloaluminophosphate molecular sieves, preferably modified silicoaluminophosphate molecular sieves, as well as to the use of these modified molecular sieves in catalytic processes, such as processes for the conversion of oxygenated hydrocarbon feedstocks.