Variations in the structure of dealuminated zeolite Y upon its treatment with boron- and phosphorus-containing modifiers were determined by X-ray diffraction and high-temperature benzene-vapor adsorption techniques. It was found that repeated treatment of the zeolite with phosphorus trichloride leads to a slight decrease in the unit cell parameters, which correlates with the variation in IR spectrum noted previously. The X-ray diffraction and adsorption data confirm the presence of impurities in the zeolite specimen that have been formed by dealumination according to the given procedure.