In vivo adipose tissue quantification is an important tool to characterize phenotypes of obesity, especially in the human. The amount and distribution of adipose tissue is associated with many of the adverse consequences of obesity. Recent studies suggest that adipose tissue is not a single homogeneous compartment. Regional adipose tissue depots vary in biological functions and individual adipose tissue compartments have stronger associations with metabolic conditions than does total adipose tissue mass. Currently there is intense and increasing interest in regional adipose tissue compartments. Computed tomography and magnetic resonance imaging often are used to quantify adipose tissue volumes or cross-sectional adipose tissue areas. Other modalities, including dual-energy absorptiometry and magnetic resonance spectroscopy, provide whole-body or regional fat measures instead of adipose tissue mass quantification.