Nasosinusal polyposis in the pediatric population is uncommon and its etiology is unclear. In this eleven-year retrospective study, we describe the etiologic features and evaluate the effectiveness of endoscopic sinus surgery in 49 children. Patients were divided into three groups according to whether nasosinusal polyposis was either isolated (n = 14), or associated with either asthma (n = 5) or cystic fibrosis (n = 30). An allergy was present in 10% of patients with isolated polyposis, 80% of patients with polyposis associated with asthma, and 19% of patients with polyposis associated with cystic fibrosis. The indications for surgery were disabling symptoms, specially chronic nasal obstruction, rhinorrhea and mouth breathing, and failure to respond to medical treatment. No surgical complications were encountered. Most patients reported improvement in quality of life with reduction of nasal obstruction in 83% of cases and rhinorrhea in 61%. Minor asymptomatic recurrence (i.e. a few micropolyp localized on the roof of the ethmoid cavity) was observed in 22.7% of the cases in this series, and major recurrence with the same functional symptoms as before surgery in 13.6%. However, recurrences were higher in patients with cystic fibrosis, since minor recurrence with no clinical manifestation was observed in 28.6% of cases and major recurrence in 17.8%. Endoscopic sinus surgery must be decided in collaboration with the pediatric and pulmonary physicians, and must be performed skillfully. With a mean follow-up of 4 years, results in this series are encouraging.