Objective：To investigate the diagnostic value of diffusion-weighted magnetic resonance imaging(DW-MRI)in patients with inflammatory lesions of breast．Methods：Thirty-three female patients(including twelve inflammatory lesions wtih abscess formation) pathologically proven mastitis were all examined with MR diffusion-weighted imaging(MR - DWI ) and Short T1 Inversion Recovery (STIR). All patients were scanned with diffenrent b values(b=400-0 s/mm2，800-0 s/mm2，1000-0 s/mm2 respectively) in DWI. Then the ADC value were calculated and the findings of lesions in DWI and STIR were analyzed. Results: 1. 81.82% Inflammatory exudation mostly manifested patchy or dot-linear high signal intensity and 18.18% manifested equal-low signal in STIR, 75.75% manifested scatter dot-linear high intensity in DWI and the signal intensity is lower than in STIR and the scape of the exudation is all smaller than in STIR, 24.24% manifested equal signal. All abscess manifested homegenious high signal intensity with well-defined margin in STIR and DWI. All abscess were well shown with b value increasing due to the exudation sharply lower.2. 100% inflammatory exudation were lower in signal intensity and the 84% decreased in area of exudation with the b value increasing, but most the signal intensity and area of abscess had no change，they were respectively 83.33% and 66.67% .3. Under the same b value, All the ADC values have significant differences between the abscess and the inflammatory exudation, the inflammatory exudation and the normal breast tissue , the abscess and the normal breast tissue（p<0.05）.4. There were significant differences among the ADC value of different values of the inflammatory exudation and the abscess. The lower the b value, the higher the ADC value. Conclusion: The combination of STIR and DWI is an important supplemental method for diagnosing inflammatory lesions, DWI can play important role in demonstrating the abscess.