BACKGROUND The epidemiological, pathophysiological and clinical links between upper and lower airways are nowadays clearly demonstrated. Most of asthmatics are suffering from rhinitis while up to 40% of rhinitic patients have asthma. Asthmatics and COPD patients are also prone to develop concomitant chronic rhinosinusitis (CRS). This study aimed to determine the predictive value of cough for concomitant asthma in patients suffering from upper airway diseases. METHODS This cross-sectional study described a group of 143 consecutive patients suffering simultaneously from common upper and lower airway disorders. Both ENT-specialists and respiratory physicians consecutively examined the patients in Ghent University Hospital from October 2004 till October 2006. This study was based on the demographic characteristics, upper and lower airway conditions. RESULTS Forty-seven percent of the patients included in the study were males and the mean age of studied population was 43.6 years. The major complaint was chronic cough. When present, patients with chronic cough have an increased risk of suffering from a concomitant asthma in both allergic rhinitis (OR=5.8) and CRS with nasal polyps (OR=10.4), but not in CRS without polyps. CONCLUSIONS Chronic cough was found to be a key symptom of associated asthma in allergic rhinitis and CRS with nasal polyps. Interestingly, chronic cough in CRS without nasal polyps did not show the same predictive value: this suggests different pathophysiological mechanisms.