PURPOSE: With increasing prevalence of hypertension (HTN) in children and adolescent, pediatricians have become more interested in blood pressure (BP) measurements. The ambulatory blood pressure monitoring (ABPM) is known to be useful to differentiate true HTN and white coat HTN. The object of this study is to assess the clinical usefulness of ABPM in Korean children and adolescents. METHODS: A retrospective review of 51 patients in Kyungpook National University Hospital from January 2002 to February 2010 was done. All patients were 6-18 years old and underwent ABPM. We calculated the mean value of ABP, BP load, nocturnal dip and compared the results with the patients' diagnosis and characteristics. RESULTS: The mean age of the 51 patients was 17.8+/-1.8 years and 19 children were obese. 37 patients (72.5%) were truly hypertensive and 1 patient was diagnosed as masked HTN and 7 children (14%) as white coat HTN. The rest of the patients were normotensive. Among patients with white coat HTN, 5 were in a prehypertensive state. Mean systolic and diastolic BP load of patients with true HTN were significantly higher than non-hypertensive children (P<0.001). Although the nocturnal dip of all patients were below 10%, there was no statistical significance. The obese patients showed higher systolic and diastolic BP. Their systolic and diastolic BP load were significantly higher than non-obese patients (P<0.001). CONCLUSION: ABPM in children and adolescents seems to be a valuable tool in the assessment of white coat HTN and in the confirmation of true HTN. A considerable number of white coat HTN patients are revealed to be in a prehypertensive state and need close follow-up.