Abstract Introduction The accurate assessment of the blood pressure (BP) allows to diagnose of the cardiovascular diseases and correct their treatment timely. Cuff-less BP measurement can be more convenient to use and can also provide the blood pressure monitoring using with telemedicine. In this study, we evaluated the cuff-less BP measurement method based on photoplethysmography. Purpose To evaluate the accuracy of cuffless blood pressure measurement using with the single-channel electrocardiogram (ECG) monitor with photoplethysmography pulse wave registration. Methods The study included 500 patients aged from 32 to 88 years (mean 64±7,9 years) with arterial hypertension. We used the single-channel electrocardiogram monitor with photoplethysmography, this device looks like a phone case and records electrocardiogram (I standard lead) and photoplethysmogram (PPG) simultaneously. For each patient, blood pressure was measured using a sphygmomanometer with a cuff (3 times and the mean value was calculated). Then within 1 minute after blood pressure measurement, an electrocardiogram and photoplethysmogram were recorded for 3 minutes using the single-channel electrocardiogram monitor with photoplethysmography. ECG and PPG were recorded from the patient's fingers in a sitting position. According to the combination of the electrocardiogram signal and the photoplethysmogram signal, using a special algorithm based on machine learning, the levels of systolic and diastolic blood pressure were calculated. We compared measurement of blood pressure obtained using with the sphygmomanometer and the single-channel electrocardiogram monitor with photoplethysmography.We used the Bland-Altman method for statistical data analysis. Results In total of 1000 blood pressure measurements were obtained from 500 patients. According to the Bland-Altman analysis of systolic pressure the average discrepancy was 3,49 mmHg, the standard deviation was 4,21, the standard error of the average was 0,61. One-sampled 2-sided t-test was −0,477 (confidence interval −2.83; −4.33). The average discrepancy for diastolic blood pressure was 3,1 mm Hg, the standard deviation was 3,61 mm Hg, standard error of the average 0,52, One-sampled 2-sided t-test was −0,455 (95% confidence interval −2,64; −4,18). The correlation of the systolic and diastolic pressure using with two measurement methods was 0,89 (p=0,001) and 0.87 (p=0,002), respectively. Conclusion There is not significant difference between the results of cuffless measurement of the blood pressure by the single-channel electrocardiogram monitor with photoplethysmography and cuff-based sphygmomanometer measurement in patients with cardiovascular diseases. Funding Acknowledgement Type of funding sources: None.