Sleep disruption is a common feature both in the patients with chronic cough and in the patients with obstructive sleep apnea syndrome (OSAS). There is increasing body of evidence that chronic nocturnal cough may be related to OSAS. We describe a 59 years old, obese man (BMI 38,6 kg/m(2)) with asthma and chronic nocturnal cough not responding to the optimal anti-asthmatic treatment. On the basis of nocturnal polysomnography moderate form of the OSAS has been diagnosed and the treatment with continuous positive airway pressure (CPAP) has been started. All the nocturnal symptoms, including cough, disappeared. The effect of CPAP in preventing nocturnal cough persisted at the follow-up visit after a year since diagnosis. This case indicates that nocturnal cough may be an important symptom of the OSAS and CPAP treatment - by abolishing sleep apneas and hypopneas - may also prevent chronic cough during sleep.