OBJECTIVE: We aimed to compare the demographic, laboratory, and ambulatory blood pressure monitoring (ABPM) parameters of patients with masked hypertension (MHT), define factors predicting MHT, and determine the ABPM parameters affecting left ventricular mass index (LVMI) in obese youth. METHODS: Data of obese patients were evaluated retrospectively. Patients with ambulatory hypertension (AHT), white-coat hypertension (WCHT), MHT, or normotension (NT) were determined. Demographic and laboratory findings, office and ABPM measurements, blood pressure variability (BPV), and heart rate variability (HRV) were compared between the groups. The factors predicting MHT and the association between LVMI and ABPM, BPV/HRV parameters were analyzed. RESULTS: None of the 118 patients (M/F: 52/66) had WCHT. Three groups were formed: AHT (n: 60, 51%), MHT (n: 46, 39%), and NT (n: 12, 10%). Striae were significantly more frequent in AHT and MHT groups (P: 0.003). Cut-off levels for office BP measurements predicting MHT were 0.85 and 0.76 for systolic and diastolic BP (SBP and DBP) indexes, respectively. Most of the ABPM parameters of MHT group were as high as those of AHT group. On regression analysis, only daytime MAP had a positive (beta: 0.340; P < 0.01) and diastolic dip (beta: -0.204; P < 0.01) had a significantly negative association with LVMI. CONCLUSION: Stria and cut-off levels for office SBP/DBP indexes, which were defined for the first time in this study, may determine the patients at risk of MHT. Although BPV or HRV had no relation to LVMI, daytime MAP and diastolic dip represented independent associations with LVMI.