OBJECTIVE Knowledge on early adulthood isolated diastolic hypertension (IDH) is limited. We compared the clinical and central hemodynamic characteristics of early adulthood IDH, isolated systolic hypertension (ISH) and normotension. METHODS A total of 509 untreated young adults (18-35 years) who underwent ambulatory blood pressure monitoring (ABPM; ABPM cohort), 148 who underwent both ABPM and applanation tonometry (ABPM-tonometry cohort) and 26 newly recruited normotensives were analyzed. Their pulse wave images were analyzed after categorizing them into type A vs. B vs. C. RESULTS In the ABPM cohort (men, 86.6%), systolic-diastolic hypertension was the most common subtype (68.0%), while IDH was the rarest (5.1%). The subtype composition showed age-dependency; the proportion of IDH and systolic-diastolic hypertension increased across the age tertiles, while that of ISH declined. Patients with IDH were significantly older and shorter than those with ISH. Despite having a significantly lower 24-h average systolic blood pressure (SBP), patients with IDH exhibited discordantly high central systolic blood pressures at levels comparable to those of patients with ISH. Pulse pressure amplification was the lowest in patients with IDH and highest in those with ISH (P < 0.001), accounting for the discordance. Augmentation index differed significantly between them (P < 0.016). The waveform composition differed across the subtypes (type A vs. B/C: IDH = 61.5 vs. 38.5%; ISH = 3.0 vs. 97.0%; normotension = 30.8 vs. 69.2%, P < 0.001); the averaged waveform plots demonstrated a clear morphological disparity between IDH (type A) and ISH (type B/C). CONCLUSIONS Early adulthood IDH is a unique entity clearly distinguishable from ISH in terms of clinical and central hemodynamic characteristics.