Impacted mandibular third molar area has been a topic of interest for a long time, and one of the most investigated parameters for two reasons:1- the lower third molars are the second most frequently impacted teeth[1,2 ]. 2- the lack of space is considered to be the major cause of this.so the radiographic diagnosis for this area is an important issue for orthodontists because of it's important role in mandibular third molar eruption wich play an impact on lower arch crowding and stability of orthodontic treatment. Objective:to study the relationship between impacted mandibular third molar area morphology and mandibular length in adults with skeletal malocclusion in the sagittal plane and to investigate the effect of sex on this area in these subjects by using cephalometric radiographic.