- Background: Our aim was to determine the clinical and epidemiological features of pandemic influenza A/H1N1 in immunocompromised children with solid tumors and hematological malignancies. Patients and Methods: A prospective study was conducted during the H1N1 pandemic between August 2009 and February 2010 in a pediatric hematology-oncology unit. Demographic and clinical data were obtained from all children with suspected H1N1 infection (high fever with or without respiratory symptoms). Laboratory diagnosis of influenza A/H1N1 was performed by means of polymerase chain reaction analysis of nasopharyngeal wash specimens. Results: We identified 57 episodes of suspected influenza A/H1N1 infection in 40 children. In all episodes, children were treated with oseltamivir and antibiotics until influenza A/H1N1 results were received. Of all episodes, 13 (22.8%) tested positive for influenza A/H1N1. Two of the H1N1-positive children (15.4%) had been previously immunized against influenza A/H1N1. No differences between H1N1-positive and H1N1-negative children were noted in terms of demographic features, clinical presentation, laboratory findings, and underlying disease. Three polymerase chain reactionpositive (23.0%) children and 1 H1N1-negative (2.3%) child were admitted to the pediatric intensive care unit and were mechanically ventilated (P = 0.03). One (7.7%) H1N1-positive patient died versus none of the H1N1-negative patients (P = 0.2). The condition of all other children in both the groups improved rapidly during hospitalization. Conclusions: Febrile hospitalized pediatric oncology patients, with and without pandemic influenza A/H1N1, had a similar demographic and clinical presentation with a relatively good outcome. This was probably because of early antiviral treatment and possibly because of the relatively low virulence of the virus. Immunization should be encouraged in these patients.