Thoracic computed tomography angiography revealed a filling defect with an internal air density in the lower lobar branch of the left pulmonary artery accompanied by pleural fluid, in a patient who applied with sudden onset chest pain and dyspnoea. The filling defect remained stable after anticoagulant treatment. No progression or complications were observed in 5-year follow-up. In pulmonary embolism that does not resolve despite adequate treatment, non-thrombotic sources, particularly foreign body, should be considered.