Background: In this prospective study, we looked for correlations between anatomic variants of paranasal sinuses and chronic or recurrent sinusitis. Material/Methods: Two hundred and forty (240) patients with clinical features of chronic rhinosinusitis were examined; patients with first-onset or allergic sinusitis and pregnant females were excluded. Routine multi-slice CT of the paranasal sinuses was performed to look for mucosal disease of the paranasal sinuses, drainage pathways, and presence of anatomical variations and their relation to known sinus drainage pathways. Results: Anatomic variations were very frequent, and we classified them into four easily recognized groups: nasal septum variations, middle turbinate variations, uncinate process variations, and ethmoidal variations. Deviated nasal septum was the most frequent variation in patients with chronic or recurrent sinusitis, and it was detected in 48.8% of cases. Agger nasi cells and concha bullosa were equally frequent (30.6%), and Haller cells were detected in 11.2%. Uncinate process variations were detected in 18.1%, and the large ethmoid bulla was detected in 10%. Conclusions: The importance of anatomic variations is that they can compromise drainage pathway of the related sinus, which results in inflammatory sinus disease. Anatomical variations are not diseases on their own and may be present as incidental findings in patient with chronic sinusitis.