Abstract Purpose Febrile neutropenia and lung infections are common and potential fatal complications of pediatric cancer patients during chemotherapy. Lung ultrasound (LUS) has a good accuracy in the diagnosis of pneumonia in childhood, but there is no data concerning its use in the diagnosis and follow-up of pulmonary infection in children with cancer. The goal of this pilot study is to verify the feasibility of lung ultrasonography for the diagnosis and follow up of pneumonia in children and adolescents with cancer. Material and methods This is a prospective observational case–control monocentric study conducted in the Pediatric Hematology and Oncology Department of University Hospital of Catania in patients aged < 18 years with cancer. Attending Physician used ultrasonography to detect pneumonia in cancer children with fever. As control group, cancer patients with no infection suspicion were also tested. LUS results were compared to chest X-ray (CXR) and/or chest CT scan, when these imaging techniques were performed, according to clinical indication. Results Thirty-eight patients were studied. All underwent LUS, 16 underwent CXR, 3 chest CT. Statistical analysis showed LUS specificity of 93% (95% CI 84–100%), and sensitivity of 100%; CXR, instead, showed a specificity of 83% (95% CI 62–100%) and a sensitivity of 50% (95% CI 1–99%). Conclusion This study shows for the first time that LUS allows physicians to diagnose pneumonia in children and young adults with cancer, with high specificity and sensitivity.