This report aims to summarise the current role of Endoscopic Endonasal Surgery (EES) for skull base and cerebrospinal fluid (CSF) leakage repair, to provide some guidelines for the clinical diagnosis and technical procedures of repair, to demonstrate the limits of this approach and to discuss the Belgian experience of the recent years. Endoscopic surgery for chronic sinus disease is being performed with increasing frequency and CSF leak is an significant potential complication of this surgery, although the incidence of osteo-meningeal perforations in endonasal sinus surgery is below 1% overall. CSF leakage bears the risk of meningeal or intracranial infection and complication and therefore should be repaired as soon as recognised. Following proper localisation of the leak, repair is safely performed in most of the cases by endonasal route with the help of free mucoperiostal flaps taken from the inferior or middle turbinates. This also applies for lesions of other aetiologies. The Belgian data support the statement that the endonasal endoscopic approach is a suitable and successful technique to close CSF leaks in the vast majority of our patients.