Epidemiologic studies suggest that as many as 75% of patients with COPD have concomitant nasal symptoms and more than 1/3 of patients with sinusitis also have lower airway symptoms of asthma or COPD. Because the inflammatory response of the upper and lower airways are similar, and both sites have a similar exposure to allergens and irritants, it is not surprising that rhinitis or sinusitis would coexist with COPD. Possible mechanisms of combined upper and lower airway dysfunction include the so-called nasal-bronchial reflex, inflammation caused by smoking, mouth breathing caused by nasal obstruction, and pulmonary aspiration of nasal contents. Patients with chronic sinusitis commonly have nonspecific bronchial hyperresponsiveness, suggesting a neural reflex. Postnasal drainage of nasal inflammatory mediators during sleep also may increase lower airway responsiveness. Therapy of nasal and sinus disease is associated with improved pulmonary function in patients with COPD.