Coronary vasodilator reserve (CVR) is reduced in patients with left ventricular hypertrophy (LVH). However, it is not clear whether there is any difference between the coronary blood flow increase in LVH caused by hypertension (HTH) and that caused by hypertrophic cardiomyopathy (HCM) when the heart rate increases. In this study, 16 subjects with HTH, 10 subjects with HCM, and 10 subjects with normotension (NT) were investigated. Average peak velocities at rest, at pacing, and at dilatation were measured using a Doppler catheter placed at the left descending coronary artery to calculate coronary blood flow (CBF) and CVR. CVR at rest was identical in the HTH and HCM groups, and in both cases was lower than the resting CVR in NT subjects. There were significant differences in the CVR values at a pacing rate of 120 beats/min among the groups. These values were lowest in HCM, highest in NT, and intermediary in HTH subjects. And the percent increase in CBF in HCM at that pacing rate was higher than that in HTH (p < 0.05) or NT (p < 0.05). There was no difference in the percent increase in CBF at this pacing rate between the HTH and NT groups. The effects of elevated heart rate on the percent increase in CBF were different between the HTH and HCM groups. We conclude that cardiac hypertrophy has qualitatively different effects on coronary circulation depending on whether patients have HTH or HCM.