Carotid-femoral pulse wave velocity (PWV_cf) is promoted as a clinical marker of aortic stiffness and is a measure utilising two sites where the pulse can be obtained non-invasively. PWV_cf calculation requires subtraction of the heart-to-carotid pulse transit time from the heart-to-femoral pulse transit time. This implies that an independent increase in carotid stiffness (PWV_c) will decrease PWV_cf. This study aims to quantify the effect of age dependent increase in PWV_c on PWV_cf compared to the age dependent increase in aortic stiffness, determined as aortic PWV (PWV_a). Comparison was made by using data from previous studies reporting increase in stiffness with age of the carotid artery¹ (PWV_c=0.0009×age²-0.0465×age+6.2 m/s), femoral artery² (PWV_f=0.0443×age+7.18 m/s), and PWV_cf³ (PWV_cf=0.001×age²-0.017×age+5.49 m/s). Using these values and average distances for aortic, carotid, and femoral arterial lengths, PWV_a was calculated as a function of age (PWV_a=0.0016×age²-0.0711×age+5.43 m/s). Comparison of PWV_a and PWV_cf demonstrates that the age dependency of PWV (m/s/year) is not the same when determined from PWV_cf and PWV_a. From 20 to 55 years, PWV_cf overestimates the age dependency of PWV_a by an average of 29%. From 55 to 90 years, PWV_cf underestimates age dependency of PWV_a by an average of 17%. These findings suggest that increased carotid stiffness can compromise the potential prognostic power of PWV_cf measurements.