Introduction: In patients receiving cardiopulmonary bypass, continuous blood pressure (BP) monitoring is essential during perioperative period and radial arterial (RA) pressure can be underestimated due to vasoplegia. Objectives: To determine the efficacy of femoral arterial (FA) pressure monitoring in neonate and infants who underwent cardiopulmonary bypass. Methods: We retrospectively reviewed the surgical and medical data of 179 patients under 1 year of age between January 2010 and October 2013. We reviewed perioperative blood pressure of radial artery (RA) and femoral artery which were measured simultaneously at sequential time and all the vasoactive medications. We calculated and evaluated the difference of blood pressure according to the level of vasoactive inotrope score (VIS). Results: Mean age at surgery was 4.7±3.4 months and mean body weight was 3.5±0.6 kg. The FA catheter-related complication occurred in 5 patients (hematoma in 4 and local infection in 1). There was no significant difference between RA and FA blood pressure until 48 hours after surgery. In RA pressure, systolic and mean BP are significantly higher in lower VIS group (p=0.007, p=0.001). In FA pressure, systolic BP showed significantly higher in lower VIS group (p=0.003) Also, the gradient of diastolic and mean BP between RAP and FAP were significantly greater in higher VIS group (p=0.001, p=0.002). Conclusions: FA cannulation can be performed safely. In those with higher level of vasoactive medications, FA monitoring can be considered as more accurate method than RA monitoring probably due to vasoplegia after cardiac surgery. Further prospective studies are needed.