Morphological and functional condition of the ostiomeatal complex is a key to understanding pathogenesis of paranasal sinusitis. Multicausal obstructions of this complex disturb drainage and sinus ventilation. Connections between inflammation in the nasal cavity and in the paranasal sinuses and bronchial tree support the theory of one airway disease. A new surgical procedure in treatment of chronic sinusitis is functional endoscopic sinus surgery (FESS).