Pulmonary arterial catheter (PAC) placement under fluoroscopy is a useful and safe method to diagnose certain congenital cardiac anomalies [1]. However, when a PAC for intraoperative monitoring is placed without the aid of fluoroscopy, it may be inadvertently placed into anomalous veins. The following report presents a case of persistent left superior vena cava (PLSVC) with absence of right superior vena cava, which was not detected by a PAC inserted via the right internal jugular vein.