Objective: The aim of this study was to determine the frequency of anatomic variations of the paranasal sinuses and their roles in the development of sinusitis. Materials and Methods: Computed tomography of paranasal sinuses of 350 patients was assessed in terms of anatomic variations and inflammatory sinus pathology. The coexistence of anatomic variations with sinusitis was statistically investigated. Results: At least one anatomical variation of paranasal sinuses was detected in 325 patients (92.9%). In 297 (91.4%) of these patients, sinusitis was observed at rates varying depending on the types of anatomic variations. A statistically significant relationship was found between agger nasi cells, Onodi cells, hypertrophy of middle concha, concha bullosa, uncinate bulla, and the medial and lateral deviations of uncinate process and sinusitis. On the other hand, there was no statistically significant relationship between septal deviation, paradoxical middle concha, secondary middle concha, great ethmoidal bulla, and sinusitis. Conclusion: Certain types of paranasal sinus variations create a susceptibility to sinusitis.