Objective To evaluate the clinical impact of whole body diffusion weighted imaging (WB-DWI) on diagnosis and staging of malignant lymphoma. Methods Thirty-one patients with suspected iymphadenopathy were enrolled. WB-DWI was performed by using short TI inversion recovery echo-planar imaging sequence with free breathing and built-in body coil. Axial T2-weighted imaging images of the same location were used as reference. The results of WB-DWI were compared with pathological results and other imaging modalities. The mean apparent diffusion coefficient (ADC) values of different kinds of lymph nodes were compared. Results WB-DWI was positive in all 18 cases with lymphoma, 5 cases with metastatic lymph nodes and 4 of 8 cases with benign lymphadenopathy. The mean ADC value of lymphomatous, metastatic and benign lymph nodes was (0.87±0.17) × 10-3, (0.98 ± 0.09) × 10-3 and (1.20 ± 0.10) × 10-3 mm2/s. There was significant difference in ADC value between benign lymph nodes and other two groups (P < 0.01). The sensitivity, specificity and accuracy of WB-DWI in diagnosis of lymphoma were 100% (18/18), 30.8% (4/13) and 71.0% (22/31). When an ADC value of 1.08 × 10-3 mm2/s was used as the threshold value for differentiating malignant from benign lymph nodes, the best results were obtained with sensitivity of 87.8% and specificity of 91.3%. Sixteen of eighteen cases (88.9%) of lymphoma were accurately staged in accordance with clinical staging. Conclusions WB-DWI is a sensitive, but less specific technique for diagnosis of lymphoma. It is difficult to differentiate lymphomatous from metastatic lymph nodes using WB-DWI. However, it is a valuable imaging modality for staging of patients with malignant lymphoma.