Catalysts for converting polyalkylaiomatics to monoalkylaromatics, particularly cumene and ethyl benzene are disclosed which comprise modified Y-85 or LZ-210 zeolites. For cumene and ethylbenzene production, a disclosed catalyst, made of 80 wt % zeolite and 20 wt % alumina binder on a volatile-flee basis, has one or more of the following physical characteristics: (1) an absolute intensity of the modified Y zeolite as measured by X-ray diffraction (XRD) of preferably at least 50 and (2) a framework aluminum of the modified Y zeolite of preferably at least 50% of the aluminum of the modified Y zeolite.