Although rare, inflammatory myofibroblastic tumor is the most common primary lung mass in children. We report the case of an 11-year-old boy investigated for persistent cough and dyspnea with complete left lung atelectasis mimicking pneumonia. CT and MRI showed an endobronchial mass of the left main bronchus. The boy underwent endoscopic resection of the tumor and histology was in favor of an inflammatory myofibroblastic tumor of the lung. This diagnosis should be suspected in children with recurrent pneumonia. The prognosis is good after complete resection.