B cells arise from stem cells precursor and develop through a tightly regulated and selective process that lead to the generation of different B cell populations such as transitional, mature, memory and plasmacells. These B cell subsets can be identified using flow cytometry by the expression of specific surface antigens. The growing knowledge of the pivotal role played by B cells in the development and progression of autoimmune diseases combined with the advances in monoclonal antibody technology, led in the last years to the generation of different biological agents targeting B cells. In this context, nuclear medicine can offer the possibility to use a panel of biologic radiopharmaceuticals for molecular imaging of inflammatory diseases. Radiopharmaceuticals bind to their targets with high affinity and specificity and have an excellent imaging diagnostic potential for the evaluation of disease activity, selection and monitoring of immune therapies. Several molecules have been radiolabelled for the imaging of T lymphocytes whereas, by now, the anti CD20 Rituximab is the only biological therapy targeting B cells that demonstrated to be efficiently radiolabelled and used to detect inflammation in autoimmune patients.