Background: Ambulatory Blood Pressure Monitoring (ABPM) is useful to determine nocturnal BP. However, the major limitation is the spot-check nature. The main objective of the study is to compare the nocturnal blood pressure (BP) results derived from continuous nocturnal (beat-to-beat) finger cuff BP monitoring device (CNBPM) based on pulse decomposition analysis and from conventional arm cuff-based ABPM. Methods: We prospectively enrolled 17 subjects from the community. Each subject underwent 1 day of standard 24-hour ABPM. On a second day, the subjects underwent continuous BP monitoring at nighttime only. Systolic BPs (BP hereafter) 12 AM - 6 AM constituted nocturnal BP. We compared the maximum nocturnal BP from ABPM with that from CNBPM. For paired comparison, we matched every 30-minute nocturnal BPs by ABPM, with the corresponding 30 min-averaged nocturnal BPs from CNBPM. Using these data points, we also examined nocturnal dipping by both methods. For continuous BP dipping calculation, we used late night and early AM BP recording (outside 12 AM-6 AM window) derived from continuous BP monitoring. Non-dipping was defined by < 10% BP reduction at nighttime. Results: All enrolled subjects recorded both ABPM and CNBPM. Maximum nocturnal BP was lower by ABPM than by CNBPM ( M 71.28, SD 8.65 vs. M 96.11, SD 13.74), p<0.0001). Paired comparison of every 30 min nocturnal BP yielded a lower nocturnal BP by ABPM than CNBPM (113.65 mmHg (18.31) vs. 113.43 (SD 27.32), p = 0.978). The mean absolute dipping was similar between ABPM and CNBPM (13.2% (7) and 9.5 (10.6), p=NS) respectively. Among 8 subjects with normal dipping, 9 subjects were categorized as non-dipping by CNBPM. Among 11 subjects who had normal dipping by ABPM, 6 subjects met non-dipping by ABPM. CNBPM was better tolerated than ABPM according to subjects. Conclusion: This study demonstrates that the clusters of BP variability overnight may be missed by a spot-check nocturnal BP measurement by ABPM. There was bias toward the underestimation of BP by ABPM when compared to CNBPM. Further studies should determine a subset of high-risk patients who may benefit from using CNBPM for accurate nocturnal BP monitoring.