Although the white-coat effect (WCE) is not rare, its detection is often difficult in treated hypertensive patients. The aim of this study was to elucidate the factors that affect and predict the WCE in treated hypertensive patients in Korea. A total of 1087 outpatients (mean age: 57 ± 10 y; 52% female) checked blood pressure in office and at home. We divided the outpatients into two groups according to the presence or absence of the WCE. Waist circumference was smaller in the WCE group. In addition, in the WCE group, the incidence of diabetes mellitus (DM) was lower, but family history of premature cardiovascular disease was higher. Target organ damage, including damage to the heart, was lower in the WCE group. Pulse pressure (PP) in the clinic was higher in the WCE group and was also positively correlated with a systolic WCE, especially when measured by a doctor (r = 0.511, P < .001). By multivariate regression analysis, PP measured by a doctor independently correlated with systolic WCE (ß = 0.573, P < .001). Our findings suggest that PP measured by a doctor at a clinic may predict the WCE, which can help in the treatment of hypertensive patients.