Obesity is predominantly caused by overeating, an abnormal behaviour for which there is no unequivocal neurophysiological explanation. Functional neuroimaging techniques, such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), have recently emerged as new tools to search for regions of the brain that are involved in the regulation of eating behaviours and those that are involved in the pathophysiology of obesity. Using these techniques, a limited number of studies have provided the first in vivo images of the human hypothalamic response to nutritional stimuli and revealed the complexity of the human brain response to hunger, taste, and satiation. Selective differences have been reported in the functional architecture of the brain of obese and lean individuals. We discuss current use and possible future developments of functional neuroimaging applied to obesity research. We conclude that functional neuroimaging provides an increasingly important tool for investigating how different regions of the brain work in concert to orchestrate normal eating behaviours and how they conspire to produce obesity and other eating disorders.