Radiolabelled cytokines and chemokines are a new group of radiopharmaceuticals. These, by binding to specific receptors expressed on selected cell populations, enable the histological and functional characterization of immune-mediated processes, in vivo. Clinical studies have demonstrated the efficacy of using this type of scintigraphy in detecting sites of acute inflammation (infection) and chronic (T-cell-mediated) inflammation. Recent studies are focusing on the possible use of radiolabelled cytokines and chemokines for the biological characterization of cancer cells in vivo. In particular, the homing of metastases into specific tissues could depend on the chemoattraction of these tissues, mediated by soluble chemokines that bind to specific receptors expressed on cancer cells. These studies will generate a deeper knowledge of the molecular mechanism of tumor metastasis and lead to new therapies in nuclear medicine.