We present three cases of air embolism after preoperative marking guided by computed tomography (CT) using the hookwire system. Case 1: A 54-year-old man complained of dysarthria and weakness of the left side of the body after CT-guided marking was successfully performed with no significant event. CT after the marking demonstrated air density in the ascending aorta. Case 2: A 64-year-old woman suddenly deeply inspired while a needle for marking was inserted near the pulmonary nodule. After the marking, she complained of weakness of the left upper limb. CT after the marking demonstrated air density in the descending aorta. Case 3: A 77-year-old man coughed during needle insertion near the pulmonary nodule. He complained of numbness in the fingers of both hands. After the marking, CT demonstrated air density in the ascending aorta. We should pay attention to the merger of air embolism in CT-guided marking using the hookwire system.