Positron Emission Tomography (PET) imaging is a well established method for obtaining information on the status of certain organs within the human body or in animals. This paper presents an overview of recent trends in PET instrumentation. Significant effort is being expended to develop new PET detector modules, especially those capable of measuring the depth of interaction. This is aided by recent advances in scintillator and pixellated photodetector technology. The other significant area of effort is in the development of special purpose PET cameras (such as for imaging breast cancer or small animals) or cameras that have the ability to image in more than one modality (such as PET/SPECT or PET/X-ray CT).