Platinum phases of fine (particle size 1–2 nm) and coarse (particle size 4–5 nm) dispersions are grown inside a NaX zeolite matrix. The cyclopentane isotherms indicate a partial lattice destruction and a generation of a secondary porous structure consisting of secondary micropores and secondary mesopores. The structural changes of the faujasite lattice accompanying the growth of platinum particles are small, provided that the number of platinum atoms per unit cell does not exceed four or five.