Objective To explore the diagnostic value of magnetic resonance whole-body diffusion weighted imaging (WB-DWI) for lung cancer, metastasis and lymph node involvement. Methods A total of 260 lung-cancer patients who were treated in our hospital from January 2018 to December 2019 were selected. All patients were diagnosed by WB-DWI. The surgical, puncture biopsy and clinical follow-up results were used as the gold-standard. Analyzed the value in the diagnosis of metastasis and lymph node involvement. Results After surgery, biopsy and clinical follow-up, the diagnosis was confirmed. Among the 260 patients with lung cancer, 50 patients had metastatic lesions, a total of 145 lesions, including 120 lymph nodes. The lymph node involved sites included 25 in the neck, 42 in the mediastinum, 25 in the abdominal cavity and 28 in the pelvic cavity. The accuracy of WB-DWI to detect lymph node involvement in lung cancer metastasis was 93.79% (136/145), sensitivity was 95.83% (115/120), specificity was 84.00% (21/25), positive predictive value was 96.64% (115/119), the negative predictive value was 80.77% (21/26). According to the consistent Kappa measurement, the results of WB-DWI diagnosis of lymph node metastasis and surgical, puncture biopsy, clinical follow-up results were highly consistent (Kappa=0.786, P=0.000), the metastatic lesions involving lymph nodes had lower apparent diffusion coefficient (ADC) values than those without lymph nodes involvement, and the exponential apparent diffusion coefficient (eADC) was higher than those without lymph nodes involvement, the difference was statistically significant (P<0.05). Conclusion The value of WB-DWI in the diagnosis of lung cancer metastasis involving lymph nodes is significant, which helps to formulate more accurate, efficient and safe treatment plans.