In this prospective multicentric study, we investigated the contribution of positron emission tomography (PET) scanning to the staging of Hodgkin's lymphoma (HL) by computed tomography (CT) and attempted to determine whether it has any impact on therapeutic approach. One hundred eighty six consecutive patients with HL from six Italian centers were enrolled in this study. They were staged with conventional methods; 2-[fluorine-18]fluoro-2-deoxy-D: -glucose PET scanning were prospectively compared to CT. CT and FDG-PET stages were concordant in 156 patients (84%) and discordant in 30 patients (16%). PET stage in comparison to CT stage was higher in 27 patients (14%) and lower in 3 patients (1%). The programmed treatment strategy was modified in 11 out of 30 patients (37%) after the definition of final stage. If we considered the 123 CT staged patients with localized stage, ten patients (8%) with a change of stage from localized to advanced after PET evaluation were treated with different strategy. FDG-PET was shown to be a relevant, non-invasive method that supplements conventional procedures and should therefore be used routinely to stage HL, particularly in early stage patients, where a change in stage may modify disease management.