Background: Non-Hodgkin lymphoma (NHL) is a neoplasm of the lymphoid tissues arising from B cell precursors, T cell precursors, mature B cells, and mature T cells. NHL accounts for one of the most common malignant diseases in the general population. Objective: To assess the importance of positron emission tomography/computed tomography (PET/CT) in the initial staging and evaluation of therapeutic response in patients with NHL. Patients and methods: Thirty cases, confirmed by histopathology to be NHL, were examined by PET/CT for initial staging and evaluation of therapeutic response. Results: PET/CT detected 94 total involved sites with sensitivity 100 %, specificity 97.6 %, and accuracy 98.2 % which was larger than sites detected by CT; 80 total involved sites with sensitivity 84.04 %, specificity 91.5%, and accuracy 89.7 %. Regarding to treatment response assessment, PET/CT detected complete regression (60%), partial regression (30 %) stationary course (0%) and progression (10 %) while CT detected complete regression (70%), partial regression (20 %) stationary course (10%) progression (0%). Conclusion: PET/CT provides more accurate results regarding the staging and treatment response of patients with NHL in comparison with CT declaring a greater sensitivity, specificity, and accuracy.