The objective of this study was to determine the integrity of the homoeostatic coupling relationship between neuronal electrical function and cerebral metabolism in the vegetative and minimally conscious states. Ten patients who met recognised diagnostic criteria (six in the vegetative state and four minimally conscious) were investigated using simultaneous electroencephalography and positron emission tomography. It was found that the coupling between neuronal electrical activity and regional glucose metabolism was preserved in all the minimally conscious patients but was absent in all the vegetative state patients. Our preliminary results suggest patients in the vegetative state may endure an impaired coupling relation between neuronal electrical function and cerebral energy metabolism.