Abstract : Clear rhinorrhoea is a common symptom in patients with obstructive sleep apnoea (OSA), which may worsen with nasal continuous positive airway pressure treatment (nCPAP). However, rhinorrhoea can also be the presenting symptom of cerebrospinal fluid (CSF) leak, which is due to a communication between the subarachnoid space and the nasal cavity or sinuses. We report another case of a patient with OSA in whom CSF leak developed following the initiation of nCPAP treatment.