A dentigerous cyst is an odontogenic cyst that develops from reduced enamel epithelium and is associated with the crown of an impacted tooth. It is the second most common cyst after radicular cysts. It is mostly seen in the second and third decades of life and is rarely encountered in children. Dentigerous cysts are most common in mandibular molars, and are rare in premolars and canines. They are usually asymptomatic, unless they are secondarily infected. Cone beam computed tomography (CBCT) is a state-of-the-art three-dimensional imaging modality used in all areas of dentistry specifically for maxillofacial imaging. Because of its features, the role of CBCT has been extended from diagnosis to surgical management. This report describes a case of a dentigerous cyst in a 12-year-old patient involving an impacted right mandibular second premolar, a rare entity. Using CBCT, canal mapping was performed to extricate the extension of the cyst with the mandibular canal, helping the surgeon during surgical management. The present report also highlights the role of CBCT in the preoperative assessment and management of dentigerous cysts.