One hundred and seventy-five hemato-oncologists and nuclear medicine specialists from 23 countries joined the 2-day 4th International Workshop on Positron Emission Tomography in Lymphoma held in October 2012. The meeting was under the auspices of the European Lymphoma Institute, the Lymphoma Study Association (LYSA) and Fondazione Italiana Linfomi (FIL). Thirty-nine scientific posters were presented or discussed in the plenary session. A group of nuclear medicine and radiology experts presented and discussed with the audience their final report on lymphoma staging and restaging with positron emission tomography (PET). The same report will be presented in a dedicated workshop during the 12th International Conference on Malignant Lymphoma (ICML) in Lugano. Mainly, it was proposed to use the same type of criteria (Deauville five-point scale) for interim and end of treatment PET reporting. Results were presented on the state of the art of the role of PET in staging and response assessment in follicular lymphoma, mucosa-associated lymphoid tissue (MALT) lymphoma, primary mediastinal large B-cell lymphoma (PMBCL), mantle cell lymphoma and T cell lymphoma. Although PET is now recognized as a useful tool in follicular lymphoma, prospective data should be acquired on a larger scale to better define its role in the other subtypes. Technical and clinical focus was given to the measurement of metabolic volume to evaluate the total tumor burden, and interim PET-based ongoing trials were presented for LYSA and FIL. Final results of international validation studies of Deauville criteria and change in maximum standardized uptake value (ΔSUVmax) analysis were presented for Hodgkin lymphoma and diffuse large B-cell lymphoma. A closed meeting was held addressing the issue of contrast-enhanced computed tomography (CT) in the PET/CT era. The next meeting (September 2014) will be open to all imaging modalities used for lymphoma investigation.