The purpose of this study was to evaluate the morphological changes in the TMJ after mandibular body lengthening by distraction osteogenesis (DO). This study was conducted on 10 patients suffered from unilateral mandibular body deficiency and corrected through mandibular lengthening following standard distraction osteogenesis (DO). The impacts of DO on TMJs were examined and evaluated with magnetic resonance images through pre-operative- and post-distraction. The results revealed that; comparing pre-operative and post-distraction interpretation of TMJs magnetic resonance images; there was no morphological effect on TMJ following mandibular body distraction osteogenesis; on the other hand there was improvement of 4 cases suffered from anterior disk displacement with reduction (ADDWR) following mandibular body lengthening by distraction osteogensis (DO).