Life expectancy is still reduced in aortic coarctation (AoC) patients despite a successful repair because of late arterial hypertension and atherosclerosis. Masked hypertension (MH) consists of an elevated daytime or awake ambulatory blood pressure (BP) in the presence of a normal BP on conventional measurement at the office. To assess the prevalence of MH among AoC normotensive young patients successfully treated and to evaluate the impact of MH on left ventricular (LV) geometry and function.We studied 76 AoC patients (mean age 14.5 ± 5.7 years, male 64%). According to 24 h ambulatory BP monitoring (ABPM) our sample was divided in real normotensive patients (Group RN,n=40) and MH patients (Group MH,n=36). There was an increased pressure gradient in the aortic arch (15mmHg ± 4 vs 13mmHg ± 4.7,P<0.05), increased LV mass (51 g m−2.7 ± 13 vs 46 g m−2.7 ± 12,P<0.05), in MH AoC patients. Regional longitudinal deformation properties of the basal septal segment (-15% ± 2.4 vs -20% ± 5,P<0.01) and LV twist values (14° ± 1.6 vs 12°±1.9,P<0.0001) were reduced in the MH group. There is a high prevalence of MH in young patients with repaired AoC, which is associated with abnormal LV structure and function. Clinicians should consider 24 h ABPM measurements in apparently normotensive patients followed up for AoC repair.