We compared classic ECG-derived versus a mobile approach to heart rate variability (HRV) measurement. METHODS & RESULTS: 29 young adult healthy volunteers underwent a simultaneous recording of heart rate using an ECG and a chest heart rate monitor at supine rest, during mental stress and active standing. Mean RR interval, Standard Deviation of Normal-to-Normal (SDNN) of RR intervals, and Root Mean Square of the Successive Differences (RMSSD) between RR intervals were computed in 168 pairs of 5-minute epochs by in-house software on a PC (only sinus beats) and by mobile application "ELITEHRV" on a smartphone (no beat type identification). ECG analysis showed that 33.9% of the recordings contained at least one non-sinus beat or artefact, the mobile app did not report this. The mean RR intervals were significantly longer (p鈥?鈥?.0378), while SDNN (p鈥?鈥?.0001) and RMSSD (p鈥?鈥?.0199) were smaller for the mobile approach. CONCLUSIONS: Measures of identical HRV parameters by ECG-based and mobile approaches are not equivalent.