Background: Patients with masked hypertension tend to have a higher risk than white coat hypertension. But there are few data showing the real characteristics. Therefore, we evaluated the characteristics of masked hypertension in patients receiving medical treatment for hypertension. Methods: We enrolled 1,021 out-patients (mean age: 56짹10 years, 488 males) with diagnosed of hypertension who did not change oral anti-hypertensive medication for 6 months. Office BP (blood pressure) was checked by nurse and doctor twice per visit. Home BP was checked in every morning and evening for 2 weeks. We compared the characteristics between masked hypertension and white coat hypertension patients group. Results: There were 107 (10.5 %) patients with masked hypertension, and 236 (23.1 %) patients with white coat hypertension. Mean office BP was 130/80 mmHg, whereas home BP was 137/86 mmHg in masked hypertension. In white coat hypertension, mean office BP was 149/86 mmHg and mean home BP was 124/75 mmHg. Age and gender was not differet between two groups. Body weight (68짹10 vs. 65짹10 kg), body mass index (25짹3 vs. 24짹3), waist (89짹9 vs. 86짹9 cm) and hip circumference (99짹6 vs. 97짹6 cm) were higher in masked hypertension group. Fasting blood sugar level was higher in masked hypertension group (112짹37 vs. 104짹16 mg/dL, p=0.009). Family history of premature cardiovascular death (p=0.02) and heart damage (p=0.03) such as left ventricular hypertrophy, angina, prior myocardial infarction and heart failure were more frequent in masked hypertension group. Angiotensin converting enzyme inhibitor (p=0.01) and alpha blocker (p=0.02) were more commonly used in masked hypertension group, whereas beta blocker (p=0.02) in white coat hypertension group. Conclusion: Metabolic risk was more closely related with masked hypertension than white coat hypertension. Home BP measurement was an useful tool of discrimination of masked hypertension in patients with hypertension.