The purpose of this study was to determine whether regional myocardial glucose use in patients diagnosed as having hypertrophic cardtomyopathy (HC) at a younger age differs from that in those diagnosed at middle to old age. Sixteen patients with HC (group 1 aged <40 years (n = 8); group 2 aged >40 (n = 8) were studied using positron emission tomography and fluoro-18 2-deoxyglucose (FDG). AN patients were diagnosed as having HC within 6 years of the study. Contiguous regions of interest were selected circumferentially on each cross-sectional image of the left ventricular wall. In each region of interest, % FDG fractional uptake was calculated. In each patient, % left ventricular FDG fractional uptake was determined as a mean value of % FDG fractional uptake in each region of interest. Moreover, as a measure of nonhomogeneity, the % interregional coefficient of variation in FDG fractional uptake was calculated in each patient. Whereas % left ventricular FDG fractional uptake did not differ between the 2 groups, the % Interregional coefficient of variation in FDG fractional uptake was increased in group 1 compared with that in group 2 (11.5 ± 3.6 vs 7.4 ± 1.6%; p <0.02). Interventricular septum/left ventricular posterior wall thickness ratio and total counts in cross-sectional image did not differ between the 2 groups. These data suggest that patients diagnosed as having HC at a younger age have more nonhomogeneous myocardial metaboNc characteristics than do patients diagnosed at middle or old age, and support the notion that HC in the young may be different from that in the middle-aged or elderly.