Patients with aortic coarctation (CoAo) often have a diastolic flow in the descending aorta. The effect of arterial stiffness on CoAo flow pattern was described in vitro and with computer models. Study of Doppler flow patterns and arterial stiffness may provide helpful data to support the decision of CoAo treatment. Fifty studies were obtained in 31 patients (14 women, 21.5 ± 15.5 years). In 19 patients, studies were performed before and after percutaneous intervention. Systolic invasive gradients were measured (Sgrad). Doppler parameters included Doppler corrected gradient (Dgrad), diastolic velocity at end of T wave (DVT), end diastolic velocity (DVQ), systolic and diastolic half pressure times (SHPTc and DHPTc) and velocity runoff (VRc). In 19 patients, before intervention, arterial stiffness was assessed by measuring pulsed wave velocity (PWV) between right carotid and radial arteries. Sgrad showed correlation with Dgrad, DVT, DVQ, SHPTc, DHPTc and VRc (p < 0.01). Using multiple regression models, Sgrad variability was best explained by combining the variables Dgrad and DHPTc (R ² = 0.766). A variable named DTail was obtained with DTail = 1 if DHPTc > 0. In the group with Sgrad below 30 mmHg, a negative correlation was found between DTail and PWV (p = 0.024), suggesting that low aortic stiffness contributes to persistent diastolic flow in the descending aorta. Doppler systolic and diastolic parameters correlated well with severity of CoAo. In mild to moderate CoAo, Doppler diastolic flow in the descending aorta was more likely in patients with lower arterial stiffness.