Resting cerebral glucose metabolism was assessed by PET using FDG in eleven Down syndrome (DS) patients. Standardized uptake values (SUV) were determined on a pixel by pixel basis from the measured tissue FDG-activity data. The results showed that the mean value of the global FDG-uptake in the DS patients was not significantly different from the one obtained in the control group consisting of children and young adults. The standard deviation of SUV, however, was much higher in the DS group in almost all regions. The statistical parametric mapping (SPM) method was applied to compare the relative cerebral FDG accumulation pattern of the populations. Six regions (clusters) were found in which the glucose-uptake was higher in the DS patients than in the control group. The anatomical localization of these clusters was based on MRI investigations and brain-atlas technique.