The reliability of blood pressure measurement with wrist devices, which has not previously been assessed under real-life circumstances in general population, is dependent on correct positioning of the wrist device at heart level. We determined whether an error was present when blood pressure was self-measured at the wrist in 721 unselected subjects from the general population. After training, blood pressure was measured in the office and self-measured at home with an upper-arm device (the UA-767 Plus) and a wrist device (the UB-542, not provided with a position sensor). The upper-arm−wrist blood pressure difference detected in the office was used as the reference measurement. The discrepancy between office and home differences was the home measurement error. In the office, systolic blood pressure was 2.5% lower at wrist than at arm (P=0.002), whereas at home, systolic and diastolic blood pressures were higher at wrist than at arm (+5.6% and +5.4%, respectively; P<0.0001 for both); 621 subjects had home measurement error of at least ±5 mm Hg and 455 of at least ±10 mm Hg (bad measurers). In multivariable linear regression, a lower cognitive pattern independently determined both the systolic and the diastolic home measurement error and a longer forearm the systolic error only. This was confirmed by logistic regression having bad measurers as dependent variable. The use of wrist devices for home self-measurement, therefore, leads to frequent detection of falsely elevated blood pressure values likely because of a poor memory and rendition of the instructions, leading to the wrong position of the wrist.