Recent successful zeolite structure determination based on electron diffraction and image analysis data shows interesting prospects to characterize zeolitic frameworks provided the crystals are thin enough to produce useful crystallographic phases from image analysis. Zeolite SSZ-25 and porosil ITQ-1 structures were compared to reveal if they are isomorphous to MCM-22 zeolite. By using electron microdiffraction intensity data in the [0001] axis and phases extracted from HREM images taken at different defocus conditions, the resulting projected [0001] potential maps are found to be very similar for both structures and close to that of the MCM-22 zeolite.