Introduction: Through cone beam computed tomography, alterations in the maxillary sinuses, such as opacities, space occupation and thickening of the mucosa, can be observed. Some factors contribute to this thickening, standing out among dental factors, periodontitis, apical pathology and endodontic treatments. Objective: To evaluate the association between changes observed in the maxillary sinuses and apical lesions using cone beam computed tomography. Materials and methods: It was a descriptive study with a retrospective and cross-sectional, correlational, field, non-experimental design. The sample consisted of 115 tomographic volumes obtained using Planmeca ProMax 3D Classic equipment (Planmeca, Helsinki, Finland). The presence/absence of endodontic treatment in the present posterior teeth, presence/absence of periapical lesion associated with these teeth, the size of the periapic...