Aim of study: was to evaluate the skeletal and dental effects of maxillary expansion by alternate rapid maxillary expansions and constrictions technique in comparison to conventional RME expansion by Hyrax by using PA cephalometry. Material and methods: Twenty patients with constricted maxillary arch represented with an unilateral or bilateral posterior cross bite were selected with ages ranged from 12-15 years. Patients were divided randomly into two equal groups by computer aided randomization according to the protocol of expansion into (Group I): who received alternate rapid maxillary expansions and constrictions (Alt-RAMEC) protocol and (Group II): who received conventional RME protocol. Results: Skeletally, the Latero-Nasal Width and the Maxillary width recorded higher mean values in Alt-RAMEC group than RME group with statistical significance. Dentally, all linear and angular measurements recorded higher mean values postoperatively in Alt-RAMEC group than RME group with no statistical significance except upper inter-incisal width mesial. Conclusions: Alt-RAMEC protocol produces highly skeletal effects by increasing the nasal width and the maxillary width.