Cuffless blood pressure (CL-BP) measurements are believed to be a potentially alternative to cuff-occlusion-based (C-BP) measurement. A new cuffless device was developed for ambulatory BP monitoring. We assessed the accuracy of a new CL-BP device compared to a standard oscillatory C-BP device over the 24 h. Eighty-four consecutive patients were included in the study. BP was measured simultaneously by the CL-BP device and by a C-BP device over the 24 h. Calculations included 24 h mean systolic (S) BP, the mean diastolic (D) BP and the heart rate (HR). Correlations between the CL-BP and C-BP measurements were sought using Pearson's correlation coefficients and Bland-Altman plots. Using the C-BP device, the 24 h SBP value for the cohort was 125.4 ± 10.9 mmHg (mean ± SD); the corresponding DBP value being 75 ± 8.3 mmHg. Mean SBP/DBP were higher with the CL-BP device, i.e. 131.1 ± 15.9/80.2 ± 9.7 mmHg . The correlation coefficients between the two sets of values were significant (SBP: r = 0.58, DBP: r = 0.65). Better correlations for SBP and DBP were found 1) in patients with BMI > 25 (SBP: r = 0.65, DBP: r = 0.70) compared to those with BMI <25 and 2) in males compared to females (SBP: r = 0.71, DBP: r = 0.77). In our patients a CL-BP device estimated 24 h mean SBP and DBP differently from the classical oscillometric device, with a moderate correlation. CL-BP measurements were most accurate on male and overweight subjects.