We report on a case of a 7-year-old girl admitted for pneumonia not responding to oral antibiotics. During hospitalization, her pulmonary status deteriorated as a result of significant atelectasis. An extensive workup revealed an anaplastic large-cell lymphoma with neoplastic cells, found in both a biopsied lymph node and pleural fluid aspirate. Bronchoscopic examination showed nearly complete obstruction of the left side by bronchial casts composed of tumor cells, fibrin, and necrotic material, consistent with plastic bronchitis. Neoplastic infiltration of the bronchi should be considered in the differential diagnosis of disease entities causing plastic bronchitis in children.