The patient was a 57-year-old man with lung cancer. He was referred to nuclear medicine department for the evaluation of bone metastases. Bone scintigraphy was performed with 99mTc-labeled HDP. An abnormal photopenic area around the heart was seen on blood pool images. Delayed image of the thorax was normal. Chest x-ray study and echocardiography were performed to reveal the abnormality. Asymptomatic pericardial effusion was diagnosed in the corresponding area.