Objective: The aim of our study was to investigate the value of Diffusion-weighted MR imaging (DWI) for evaluating differential diagnosis of pulmonary isolated lesions. Methods: Twenty-seven consecutive patients enrolled in this study,all of whom underwent single direction DWI examinations and Received a histologic and clinical diagnosis. Diffusion factor B value was 300, 500, 800 s/mm2, respectively. DWI images of twenty cases could be satisfied to measurement and diagnosis and success rate was percent 74. Among these, lung tuberculoma 5 cases, harmatoma 3 cases, peripheral lung cancer 12 cases. The apparent diffusion coefficient (ADC) values of the lesions were measured. Statistical analyses were performed with the independent samples t test for comparing difference of ADC values between malignant nodules and benign nodules at different B value. Results: DWI images of twenty cases could be satisfied and its success rate was percent 74. When B value was 300 s/mm2, ADC values of malignant nodules and benign nodules were 0.002192 ± 0.0006091 mm2/s, 0.002454± 0.0007892 mm2/s, respectively, and P = 0.442. When B value was 500 s/mm2, ADC value of malignant nodules and benign nodules were 0.002065 ± 0.0006769 mm2/s, 0.002871 ± 0.0007746 mm2/s, respectively, and P = 0.033. When B value was 800 s/mm2, ADC value of malignant nodules and benign nodules were 0.001646 ± 0.0004292 mm2/s, 0.002651 ± 0.0008041 mm2/s, respectively, and P = 0.009. There were the most different between malignant nodules and benign nodules at B value 800 and statistical significance. Conclusion: Lung DWI imaging is helpful to diagnosis and differential diagnosis between malignant and benign isolated nodules. The ADC value of benign lesions was statistically higher than that of malignant tumors.