The ultimate goal of mandibular reconstruction is to return the patient totheir previous state of function. So the reconstructive surgeon must attempt torestore bone continuity and facial contour, maintain tongue mobility, preservation of lip competence, optimal speech articulation, restore sensation to denervated areas and the best masticatory function to enable the patient to enjoy a relatively normal diet. In this study, patients were divided into two groups (6 patients for each group):Group I, include surgical removal of benign mandibular lesion with immediate reconstruction of the defect by free anterior iliac free bone graft.Group II, include surgical removal of benign mandibular lesion with delayed reconstruction of the defect by free anterior iliac free bone gra6 a6er 4-6 months. Follow up to viability of the grafts were done in first and three month postoperatively using three phase bone scintigraphy with Single Photon Emission Computed Tomography (SPECT).The results showed increase the uptake of the tracer at graft edges with the appearance of photopenic area representing the bone graft after one month postoperative. While at three months the photopenic areas in all cases were markedly reduced. SPECT in association with clinical assessment. is a highely sensitive technique in detection of bone graft viability. Also, we follow up the bone graft using panoramic radiograph atone and six months postoperatively by measuring the surface area at different parts of the graft and relative bone density using bone gray scale (Roi).