Accurate characterization of lymph nodes in patients with cancer and in patients who present with unexplained lymphadenopathy is of major importance for appropriate treatment planning and determination of prognosis. Size measurements are still the most frequently used method for discriminating malignant from non-malignant lymph nodes, but are insufficiently accurate. In order to improve evaluation of lymph nodes, there is a need for imaging modalities that go beyond anatomical lymph node assessment and that allow visualization and quantification of physiological and biochemical processes at the cellular level. We review and discuss functional imaging techniques in the evaluation of lymph nodes.