Background: Immunosuppressive therapy places pediatric patients at risk of developing life-threatening sinonasal infections. Diagnosis and treatment are challenging owing to nonspecific signs and symptoms. The aim of this study was to present our department's experience with the surgical management of acute rhinosinusitis in immunosuppressed children. Methods: The records of all children with a hematologic or oncologic disease who underwent endoscopic sinus surgery (ESS) for acute rhinosinusitis from January 2005 to May 2014 were reviewed. Data were retrospectively collected on demographics, clinical and imaging characteristics, microbiology, pathology, treatment and outcome. Results: Thirty-four-immunosuppressed children underwent ESS for acute rhinosinusitis. Most patients had a fungal infection. Nineteen patients died at the end of follow-up; 10 deaths were infection-related. Facial swelling was the only symptom that correlated with death of infection. Relapse of the underlying disease, bone marrow transplantation, and long duration of neutropenia correlated with infection-related mortality. Fungal infection, and specifically Aspergillus, correlated with death from infection. Conclusions: ESS is a safe and efficient procedure for diagnosing and treating immunosuppressed pediatric patients with acute rhinosinusitis. Early detection and aggressive medical and surgical treatment, with control of underlying risk factors, are crucial to improve outcome.