Positron emission tomography with 2-deoxy-2-[18]fluoro-D-glucose (FDG-PET) imaging has been extensively used to detect occult metastatic malignant lesions in patients with carcinoma. We describe its use in three patients with multiple myeloma, each representing a particular clinical situation in which this imaging modality offered advantages over plain radiography, computerized tomography or magnetic resonance imaging. FDG-PET provides a whole body image showing sites of occult disease. This is of particular value in patients with non-secretory myeloma, solitary plasmacytoma or for those that relapse with focal disease following autologous or allogeneic stem cell transplantation.