Sinus mucocele is rare in the paediatric age, and so far no prevalence data have been reported in children with Cystic Fibrosis (CF). Moreover, safety and efficacy of endoscopic management of sinus mucoceles has been widely proven but only in the adult population. The aim of our study was to evaluate the prevalence of this complication and the efficacy of endoscopic sinus surgery in CF patients during the initial years of life. Among the 242 CF patients born in the period between 1990 and 2001 and in regular follow up at our CF Centre, 90 patients with possible symptoms of chronic upper airways disease (CUAD) underwent a comprehensive ENT examination including rhinofibroscopy. In selected cases a CT scan of the paranasal sinuses was also performed. CUAD was diagnosed in 55/90 because of the consistent presence of nasal obstruction, combined with at least two other nasal symptoms such as chronic nasal discharge, snoring, epiphora. Diagnosis of mucoceles (five maxillary bilateral mucoceles, one maxillary unilateral, three maxillary and etmoidal mucoceles) was done by means of CT scan in 9/15 who performed the examination. Median age at the diagnosis was 4+/-0.5 years, ranging from 0.5+/-7 years, showing a prevalence of 16.4% (9/55) among patients with symptoms. Endoscopic sinus surgery was performed in all the cases. The follow-up period ranged from 3 months to 6 years with no recurrence observed. Sinus mucocele in CF population is less unusual than expected and a high degree of suspicion is needed. Endoscopic sinus surgery seems to be a safe and efficient treatment of this complication also in a paediatric population at a high risk as for the CF patients.