Background Arterial stiffness is a risk factor for cardiovascular morbidity and mortality. The relationship between the arterial stiffness and the circadian pattern of blood pressure has been controversial. The objective of the present study was to investigate the relationship between arterial stiffness by pulse wave analysis and variables of 24-hour ambulatory blood pressure monitoring (ABPM) in patients with pre-hypertension and hypertension. Methods Seven hundred and seventy three patients (442 males, 48 짹 12 year-old) with pre-hypertension and hypertension were enrolled. Blood pressure (BP) was measured at the outpatient clinic and 24-hour ABPM was performed. Using radial applanation tonometry, pulse wave analysis was performed for evaluation of systemic arterial stiffness expressed as augmentation index. ���Nocturnal dipping��� was defined as a reduction of > 10%, when compared with the daytime values, in the systolic BP (SBP) and diastolic BP (DBP) levels at night. When compared with the daytime values, reduction of < 10% in the SBP was defined as isolated systolic non-dipping, reduction of < 10% in the DBP as isolated diastolic non-dipping and reduction of < 10% in both SBP and DBP as both systolic and diastolic non-dipping. For adjustment of age, population was divided to 2 groups: old group ��� 55 year-old (n = 213, 107 males), young group < 55 year-old (n = 560, 234 males). Results Among groups, the clinic SBP and DBP, daytime mean BP of 24-hour ABPM, gender and body mass index were not statistically different. Augmentation pressure (AP), augmentation index (AI) and heart rate (75bpm) adjusted augmentation index (AI @ HR 75) showed statistically significant difference (p = 0.009, 0.018 and 0.011, respectively). Mutivariate analysis showed that isolated diastolic non-dipping was correlated with arterial stiffness expressed as AI and AI @ HR 75, only in young group (棺 = 12.6, p = 0.04 and 棺 = 7.503, p = 0.028, respectively). No statistical difference among circadian BP patterns was demonstrated in old group. Conclusion In present study, the isolated diastolic non-dipper was closely related with arterial stiffness in patients with hypertension and pre-hypertension under 55 years old. Arterial stiffness might be closely related with the pattern of non-dipping in young hypertensive and pre-hypertensive patients.