Background: Malignant lymphoma is the most common hematological malignancy accounts for approximately 8% of all adult malignancies. The aim of this work is to study the role of PET/CT in the diagnosis and follow up of Non-hodgkin lymphoma. Methods: The study was conducted on eighty patients where the diagnosis of non-hodgkin lymphoma have been pathologically confirmed, 50 males (62.5%) and 30 females (37.5%), their ages are ranged between 14 to 81 years old. All patients were examined using Siemens Bio-graph true point PET/CT scanner. These dedicated systems integrate a PET scanner with a multi-slice helical CT scanners permit the acquisition of co-registered CT and PET images in one session. Results: among the 40 patients referred for follow up assessment, their SUVmax of the initial PET/CT examination ranged from 3 – 49.0 with a mean value of 17.05 ± 11.86 SD, with a significant change (p ≤ 0.046) in their follow up examination with SUVmax ranged from 0.0 – 28.0 with a mean value of 11.73 ± 9.25 SD, There were statically significant difference between (PET/CT) staging and CECT scan staging (p < 0.001). Conclusion: PET/CT proved statistically to be more efficient in follow up studies after chemotherapy using the standard uptake value (SUV) being more related to the functional activity of the residual tumor cells rather than to the size of the tumor itself.