A process for dewaxing of petroleum fractions involves contacting a petroleum fraction charge under appropriate dewaxing conditions with a catalyst containing a zeolite of the MFI structure or a silica with MFI framework topology, the zeolite or the silica having been synthesized in a fluoride medium and having a fluoride content between approximately 0.02 and 1.5% by weight and being characterized by an X-ray diffraction diagram as shown in Table 1 of the specification, a matrix and at least one group VIII or VI B metal of the periodic classification of elements.