The anatomic proximity of maxillary posterior teeth to the maxillary sinus provides a natural conduit for the spread of dental pathology into the maxillary sinus. This diffusion results in the development of sinus disease attributable to endodontic pathology, and is termed "maxillary sinusitis of endodontic origin" (MSEO). Ultimately, suspicion of odontogenic causes of sinus disease should come as a relief to the provider and patient alike as the conditions are very treatable by noninvasive means with high expected success. This article reviews the diagnosis and management of odontogenic sinusitis with an emphasis on CBCT imaging as part of the interdisciplinary diagnostic workup. Illustrative cases documenting the treatment of MSEO are also presented.