BACKGROUND The relationship between office vs. ambulatory blood pressure (BP) indices are well-studied in patients with essential hypertension and based on these data, it is known that the average 24-h ambulatory BP is typically lower than office BP. However, emerging data show that office SBP underestimates arterial afterload in patients with coarctation of aorta (COA), and a minimal increase in stroke volume during low-intensity exercise results in an exaggerated rise in SBP as compared to those with essential hypertension. We hypothesized that COA patients will have higher ambulatory SBP and a higher prevalence of masked hypertension compared to patients with essential hypertension. METHODS Case-control study of 118 COA patients and 118 patients with essential hypertension matched by age, sex, BMI and office SBP. RESULTS Although both groups had similar office SBP (132 ± 17 mmHg) by design, the COA group had paradoxical increases in 24-h ambulatory SBP (135 ± 14 vs. 126 ± 13; P < 0.001) and daytime ambulatory SBP (142 ± 16 vs. 130 ± 13; P < 0.001), and less nocturnal dipping (-3 ± 5 vs. -9 ± 4; P < 0.001). The COA group also had a higher prevalence of masked hypertension [36 (31%) vs 14 (12%); P < 0.001), and worse arterial function indices. CONCLUSIONS These findings underscore the potential limitations of relying on office SBP for screening/monitoring of hypertension in COA and potential pitfalls in extrapolating essential hypertension guidelines recommendations to the treatment of COA. It also provides the rationale for further studies to determine if pharmacologic BP interventions guided by ambulatory BP data will improve clinical outcomes in the COA population.