BACKGROUND: The functional significance of an intermediate coronary lesion is crucial for determining the treatment strategy, but age-related changes in cardiovascular function could affect the functional significance of an epicardial stenosis. The aim of this study was therefore to investigate the impact of age on fractional flow reserve (FFR) measurements in patients with intermediate coronary artery disease (CAD). METHODS AND RESULTS: Intracoronary pressure measurements and intravascular ultrasound (IVUS) were performed in 178 left anterior descending coronary arteries with intermediate stenosis. The morphological characteristics and FFR of 91 lesions in patients <65 years old were compared with those of 87 patients >/=65 years old. There was no difference in lesion location, diameter stenosis, minimum lumen area, plaque burden, or lesion length between the 2 age groups. Elderly patients had higher FFR (0.81+/-0.06 vs. 0.79+/-0.06, P=0.004) and lower FFR, defined as the difference between resting Pd/Pa and FFR (0.13+/-0.05 vs. 0.15+/-0.05, P=0.014). Age, along with the location and degree of stenosis, was independently associated with FFR and FFR (beta=0.162, P=0.008: beta=-0.131, P=0.043, respectively). CONCLUSIONS: Elderly patients with intermediate CAD are more likely to have higher FFR and lower FFR, despite a similar degree of epicardial stenosis, compared with younger patients. (Circ J 2016: 80: 1583-1589).