Ectopic eruption of tooth has been reported in the nasal septum, chin, palate, coronoid process and maxillary sinus in the literature. A tooth may erupt maxillary sinus and present with chronic sinusitis, mucosele and cyst formation. Obstruction the osteomeatal complex, formation of cyst in the maxillary sinus, obstruction of nasolacrimal canal leading to epiphora may occur because of the anatomic variation. There may be sinonasal symptoms of sinusitis, epiphora and pain. The diagnosis of this condition can be made radiologically. If it is symptomathic treatment of ectopic maxillary tooth with dentigerous cyst is surgical removal via a Caldwell-Luc procedure. Herein we present an original image of a dentigerous cyst containing premolar tooth in the maxillary sinus. Keywords: Tooth eruption; Maxillary sinus; Dentigerous cyst Case ReportA 43-year-old man was presented with the complaints of recurrent pain and pressure in right maxillary sinus region. He had a history of recurrent sinusitis of 5 years duration. The symptoms did not resolve despite several courses of medical therapy. The past medical history was unremarkable.Findings of anterior rhinoscopy examination were normal. In the endoscopic examination mucoid secretion was seen in right middle meatus. External examination of teeth revealed normal findings. There was no history of tooth extraction. There was no swelling in maxillary region. Intraoral examination was normal. Ocular examination was normal. Findings of blood and serum biochemistry were within normal limits. A plain computed tomography (CT) scan of the paranasal sinuses was done by taking 3-mm coronal slices. CT examination of the paranasal sinuses revealed a dentigerous cyst containing first premolar tooth in the maxillary sinus. The cyst was seen to expand in the alveolar process of the maxillary bone (Figure 1). The patient did not accept the recommended surgical treatment. DiscussionMaxillary dentigerous cysts are common disorders of the maxillary sinus. Most frequently, the cysts are incidental findings on radiographs. Etiology of the disease is not clear; inflammation, infection, allergy, odontogenic and rhinologic factors are believed to play role.