Objective To compare the diagnostic value of diffusion-weighted imaging (DWI) and MSCT in solitary pulmonary lesions; to explore prospectively the value of DWI in the distinguishing benign and malignant solitary pulmonary lesions. Material and Methods 38 patients with solitary pulmonary lesions detected by chest CT were recruited. 30 of which were peripheral lung cancer and 8 were infectious lesions which were all confirmed by biopsy. All patients were performed DWI MRI scans 1 week before operation or treatment with b values of 0 and 600s/mm2 , and the apparent diffusion coefficient (ADC) of lesions were measured. Receiver operating characteristic curve was used to analyze and derive the optimal threshold of ADC, and accuracy rate of CT and MRI was compared. Results 33 out of the 38 patients were diagnosed correctly by CT (86.84%). The ADC value in 30 cases of peripheral lung cancer was (1.15±0.13)×10- 3 mm2 /s, the ADC value in 8 cases of lung infectious granuloma was (1.45±0.20)×10- 3 mm2 /s. When b was 600 s/mm2 , the area under the ROC of the ADC values was 0.917. The cut-off of ADC value in differential diagnosis of peripheral lung cancer and infectious granuloma was 1.35×10-3mm2 /s.The sensitivity, specificity was 96.7％, 75.0％ respectively. 30 patients was diagnosed correctly by the ADC value (78.95%), 32 patients was diagnosed correctly by combining with unenhanced MRI and ADC (84.21%). There were no significant differences between the CT and MRI diagnostic accuracy. (P＞0.05). Conclusion The ADC value combining with unenhanced MRI can provide valuable information in the peripheral pulmonary cancer and infectious granuloma, which can be used as the effectively supplement to distinguish the benign and malignant solitary pulmonary lesions.