Objective: To analyze the radiographic characteristics of odontogenic maxillary sinusitis (OMS) using cone-beam computed tomography (CBCT) images. Material and methods: CBCT images of 205 OMS from 196 patients were analyzed. The etiologies of OMS and the situations of the etiologic teeth/roots were assessed, including the relationship between the radiographic periapical lesion and the maxillary sinus floor (MSF), periodontal disease, the previous endodontic therapy quality of the etiologic tooth/root, the integrity of the MSF, mucosal thickening. The maximum mucosal thickness and the minimum MSF thickness were measured. Results: Periapical lesion was the most important risk factor related to sinus mucosal thickening. Molars were 5.21 times more likely to be involved than premolars, whereas maxillary first molars (MFMs) were significantly higher than second molars (MSMs) to be involved (P<0.05). Mesiobuccal (23.37%) and palatal roots (20.31%) of MFMs were the common etiologic roots associated with OMS. The mean maximum mucosal thickness showed significant differences between destroyed and not destroyed MSF (P<0.05). The correlation between inadequate endodontic treatment and OMS was closest, especially poor clean and obturation (35.25%) and missed canals (31.15%). Of the missed root canals, 44.74% were the second mesiobuccal root canals of MFMs. Conclusions: The adequate root canal treatment for effective control of apical infection and the protection of the MSF integrity were important factors to decrease the occurrence of OMS.