Maxillary sinusitis is defined as a symptomatic inflammation of the paranasal maxillary sinuses. It is estimated that a total of 10-12% of all sinusitis is caused by odontogenic etiology and that it occurs more often in women than in men. Odontogenic inflammation of the maxillary sinuses is a result of dental disease, so it differs from other sinusitis in microbiology. The intimate anatomical relations of the upper molar teeth to the maxillary sinus facilitate the development and spread of periapical orinfection in maxillary sinus. Sinusitis can also occur due to odontogenic inflammatory cysts or due to mucosal injuries through mechanical causes such as root canal treatment. It can aslo occur due to the overfilling of the root canal with endodontic material, sinus perforation during extraction or due to an accidentally forced root or the entire tooth into the sinus, or improperly placed dental implants. Symptoms on the basis of which it is most often possible to diagnose odontogenic maxillary sinusitis are unilateral purulent rhinorrhea, maxillary pain, unilateral nasal congestion, postnasal drip, and headache. Differences in the symptomatology of maxillary odontogenic sinusitis and other sinus inflammations are not so significant, but unilateral symptoms occur more frequently. With a detailed anamnesis, clinical examination, radiological images such as an orthopantomogram, and CT and CBCT, which are considered the gold standard, a timely diagnosis and thus the treatment of sinusitis of odontogenic origin are facilitated. Therapy can be performed in several ways, and it includes initial removal of the infection, the use of antibiotic therapy and surgical methods, Caldwell-Luc surgery or the FESS technique. Odontogenic maxillary sinusitis can cause, but rarely, serious life-threatening complications such as endocranial complications or orbital abscess