Background: Bronchiolitis obliterans organizing pneumonia (BOOP) is a rare disease that can mimic a number of other pathologic pulmonary processes. BOOP is considered as a non specific response to different factors including bacterial, virus, fungal infections, toxic effect of drugs, autoimmune diseases, malignancies.Material/Methods:4 adolescents with the primary diagnosis of neoplasm are desribed to develop BOOP in different stages of treatment. The type and treatment of oncology disease, clinical, radiographic features, therapy and outcome of BOOP are introduced. Results: Problems in varied symptoms and radiological patterns, differentation of BOOP and metastases in case of atypical pulmonary lesions is encountered. Taking into account the described patients, a possible pathogenesis of BOOP is disscused.Conclusions: In every case of atypical pulmonary lesions in children treated with chemotherapy due to malignancies,besides the most probable metastases, BOOP should be differentited.

Keywords: Bronchiolitis Obliterans Organizing Pneumonia, children malignancies