Until several years ago there was a widely held belief that there is no functional BAT in adult humans. However, in 2009 several studies using the modern scanning technique of positron emission tomography (PET) did show active cold induced brown adipose tissue in young adult humans. PET scanning can assess the metabolic activity of brown adipose tissue in humans indirectly. This scan is in most studies combined with computed tomography (CT) scan for anatomical details. The most widely used PET tracer for this purpose is 18F-fluorodeoxyglucose (18F-FDG) for the measurement of glucose uptake. 18F-FDG scanning can be static or dynamic. Static scans provide information about the (relative) presence and activity of BAT. Dynamic scans provide actual glucose uptake rate. Glucose uptake rate however, does not provide information about the total oxidative metabolism. In fact the most important fuel of BAT are fatty acids. Therefore, the contribution of fatty acids must be estimated. Alternatively, several recent studies combined FDG-PET/CT measurements with the use of other tracers and dynamic scanning techniques: 15O-H2O for blood perfusion, 18F-THA for nonesterified fatty acid uptake, 11C-acetate for oxidative metabolism, and 15O2 for oxygen extraction. For this symposium several of the recent PET studies will be presented. First, intervention studies using static and dynamic FDG-PET/CT scans will be shown. Next, results from studies using alternative tracers will be discussed with respect to fuel oxidation, oxidative metabolism and perfusion of BAT. An estimate will be made on the actual contribution of BAT to whole body non-shivering thermogenesis. And finally, expectations on near future scanning possibilities, such as MRI, will be presented.