Central venous cannulation through the right internal jugular vein is a widely used technique, and complications due to this procedure are very rare. We report two cases of right massive hemothorax due to inadvertent puncture of a right subclavian artery. Digital subtraction angiography demonstrated a perforated subclavian artery in both cases. These were successfully treated with transcatheter arterial embolization for the bleeding points of the right subclavian arteries.