Aims: The aim of the study was to evaluate the role of three-dimensional computed tomography (3D-CT) in the assessment of temporomandibular joint (TMJ) ankylosis and its importance in treatment planning. The objectives of study were to measure and assess the mediolateral extent of ankylosis mass in 3D-CT and to compare the extent with intraoperative assessment. The study was also aimed to measure the coronoid process elongation in 3D-CT and its significance in treatment planning. Materials and Methods: This prospective study included 3D-CT evaluation of 11 patients with TMJ ankylosis during the period of February 2006-October 2007. Results: The 3D-CT assessment provided the length of the coronoid process and the relation of vital structures including maxillary artery to the ankylosed mass. Measurement of ankylosed mass also aids in preoperative measurement of the graft required to reconstruct the defect following removal of the ankylosed mass. Conclusion: Our study concludes that 3D-CT is a useful tool in the diagnosis and treatment planning of TMJ ankylosis.