Most human manual grip movements can be divided into power gripping and precision gripping, but central neural control during these tasks remains unclear. We investigated activation of the whole brain to analyze how simple hand movements are performed. The cerebral blood flow of seven healthy right-handed volunteers was measured by H2 15O positron emission tomography during right grip tasks without gripping a target object. Auditory-cued, repetitive power grips (i.e., fist making) and repetitive precision grips (i.e., opposition of the tip of the index finger and the tip of the thumb) were performed at 1.26 Hz. The areas activated during both tasks were the left primary sensorimotor cortex, caudal portion of the dorsal premotor, caudal portion of the supplementary motor area, cingulate motor area, and the right spinocerebellum and intermediate region of the cerebrocerebellum in comparison with the rest state. The analysis of power grip-precision grip tasks showed the activated peaks in the upper portion of the left sensorimotor area and right cerebellar vermis, but these areas were activated in both the tasks [(power grip-rest) and (precision grip-rest)] with uncorrected P < 0.001 as the statistical criterion. With P < 0.05 corrected as the statistical criterion, the results showed no significant activated peaks in regional cerebral blood flow. Our findings indicate no difference in brain activation between the acts of power grip and precision grip without a target object.