F-18-fluoro-deoxy-glucose positron emission tomography (PET) is a powerful tool for the imaging of aggressive B-cell lymphomas. In contrast, there is relatively little data on PET in follicular lymphoma grade 1 (FL-1) and grade 2 (FL-2). In this manuscript, we present our findings utilizing PET in treated FL-1 and FL-2. A retrospective review of patients who underwent PET examinations at our institution produced 95 PET examinations among 31 patients with FL-1 and FL-2. PET was obtained at initial staging, mid-induction and post-treatment. Results were compared with clinical follow-up. PET had high sensitivity (95%) and specificity (88%) for lesion detection in treated FL-1 and FL-2. Abnormal foci in FL-1 and FL-2 had similar intensities. Post-induction PET positive patients had shorter mean progression free survivals compared with PET negative patients (p-value < or =0.001), post-salvage PET positive trended toward shorter mean response duration compared with negative patients (p-value: 0.09). Our results indicate that PET is accurate in the diagnostic assessment of treated FL-1 and FL-2 and, post-treatment PET positive patients are likely to relapse prior to PET negative patients.