Obstructive sleep apnoea syndrome is characterized by irregular snoring during sleep, excessive daytime sleepiness and in some cases unwanted sleep attacks. The patient has a disturbed night sleep with numerous wakenings. Disturbed sleep at night causes daytime problems with attention, concentration and work performance. Furthermore, it may eventually result in errors and accidents. Excessive sleepiness sometimes necessitates the suspension of the patient's driving license. It is of importance to identify patients with obstructive sleep apnoea and daytime sleepiness, because the condition can be treated effectively. Many Danish patients are still unidentified. Diagnostic and treatment possibilities vary from one part of Denmark to another.