Osama Alabed Mela ¹, Mohamed Abdel- Monem Tawfik ², Noha Ahmed Mansour ^{3 1} BDS, Faculty of Dentistry, Almergib University, Libya. ² Professor of Oral and Maxillofacial Surgery Faculty of Dentistry, Mansoura University, Mansoura, Egypt. ³ Assistant Professor of Oral and Maxillofacial Surgery, Faculty of Dentistry, Mansoura University, Mansoura, Egypt. Abstract: Objectives: The aim of the present study is to evaluate the role of cone-beam computed tomography (CBCT) in the assessment of the relation between the mandibular canal and impacted third molars. Methods: Forty three patients seeking surgical removal of this impacted mandibular third molars were selected from the Out-Patient Clinic of Oral and Maxillofacial Surgery Department, faculty of Dentistry, Mansoura University for this study. Who showed a close relationship between the mandibular canal and the third molars on panoramic radiographs. Panoramic radiographic signs images were evaluated for interruption of the white line, darkening of the roots, Interruption of white line + darkening of root, developing of root, Deflection of the root,  diversion of the mandibular canal, and narrowing of the mandibular canal. All patients were referred for further evaluation using CBCT images to determine the course of each canal and its proximity to the roots. The statistical A Fisher's exact test was used to compare panoramic signs with CBCT findings. Results: Cone-beam computed tomography examination showed that Interruption of white line were significantly associated with contact status (residuals > ±1.69). With the absence of corticalization between the impacted mandibular third molar and the mandibular canal on panoramic radiographs. All other panoramic radiographic signs showed no association with contact status (residuals < ±1.69). Conclusions: The results of this study   panoramic radiography is an effective method for pre-operative assessment of mandibular third molars Interruption of white line observed on panoramic radiographs, as isolated finding or in association with root darkening, are effective in determining the risk relationship between the tooth roots and the mandibular canal, requiring 3D evaluation of the case. Keywords: Impacted mandibular third molar, mandibular canal, cone-beam computed tomography panoramic radiography signs.