<p class="abstract"><strong>Background:</strong> Chronic rhinosinusitis is an extremely prevalent disorder which has significant effect on quality of life of affected individual. Varied symptomatology and varied etiology of unilateral chronic maxillary rhinosinusitis requires a comprehensive approach by otorhinolaryngologist. The objectives of the study were to evaluate the causative factor of unilateral chronic maxillary sinusitis and to study clinical presentation of unilateral chronic maxillary sinusitis<span lang="EN-IN">. </span></p><p class="abstract"><strong>Methods:</strong> 50 patients with symptoms and signs suggestive of unilateral chronic maxillary sinusitis were evaluated. All were subjected to detailed clinical history, ENT examination including complete orodental examination, diagnostic nasal endoscopy, intra oral peri apical radiographs, CT scan of para nasal sinuses<span lang="EN-IN">. </span></p><p class="abstract"><strong>Results:</strong> Of total of 50 patients studied, gross deviated nasal septum (DNS) is commonest cause of chronic unilateral maxillary sinusitis followed by dental infection of upper premolars<span lang="EN-IN">. </span></p><p class="abstract"><strong>Conclusions:</strong> This study was carried out with an effort to find out etiology of unilateral chronic maxillary sinusitis as identification of etiology will help in successful outcome of the treatment<span lang="EN-IN">.</span></p>