Aim: Scanty information is available about the association of isolated daytime hypertension (IDH) and isolated nighttime hypertension (INH) with subclinical cardiac damage in the general population. We examined this issue in patients enrolled in the Pressioni Arteriose Monitorate E Loro Associazioni study. Methods: The analysis included 2021 participants with valid ambulatory blood pressure (BP) monitoring at baseline evaluation. IDH and INH were defined according to current guidelines. Subclinical organ damage was assessed by validated electrocardiographic and echocardiographic criteria. Results: A total of 1258 patients (62.3%) had daytime/night-time normotension, 376 (18.6%) daytime/nighttime hypertension, 231 (11.4%) INH and 156 (7.7%) IDH, respectively. Participants with hypertension, compared with their normotensive counterparts were older, included a higher fraction of men, had higher BMI, LDL cholesterol, triglyceride and glucose levels and exhibited a greater subclinical cardiac involvement. Furthermore, INH and IDH patients showed a similar degree of cardiac damage (i.e. left ventricular mass index: 89 ±18 vs 90±20g/m2), intermediate between normotensive (82±19g/m2) and day-night hypertensive patients (99±24g/m2). Conclusion: The present study shows that IDH and INH exert similar detrimental effects on cardiac structure. In a practical perspective, appropriate antihypertensive chrono-therapeutic approaches in these opposite ambulatory hypertensive subtypes may have important implications in cardiovascular prevention. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.