Abstract： Objective To evaluate the value of diffusion-weighted imaging (DWI) in the differential diagnosis of cystic pancreatic lesions.Methods Thirty-four cystic pancreatic lesions confirmed clinically or pathologically were collected,including 11 case of non-neoplastic pseudocyst,5 cases of simple cyst,6 cases of serous cystadenoma,10 cases of mucinous cystadenoma and 2 cases of mucinous cystadenocarcinoma.All the patients underwent routine serial MR and echo-planar DW imaging examination of the pancreas with b values of 0 and 600 s/mm2.The appearances of signal intensity of DWI with all cysts were recorded.ADC maps were reconstructed,and the ratio of the cysts and cyst-to-pancreas ADC (ADCR) were calculated.The receiver operating characteristic (ROC) curves were constructed to evaluate the diagnostic value of ADC and ADCR.Results Among all the 16 non-neoplastic cysts,2 cysts were slightly hyperintense in DWI,and 14 cysts were isointense.Among all the 18 neoplastic cysts,17 cysts appeared slightly hyperintense or hyperintense in DWI,and 1 cyst was isointense.The difference between the two groups was statistically significant (P ＜ 0.001).The ADC values of non-neoplastic and neoplastic cysts were (3.30 ± 0.30) × 10-3,(2.74 ± 0.34) × 10-3 mm2/s ; and the ADCR values of non-neoplastic and neoplastic cysts were 1.85 ± 0.20,1.31 ± 0.21,the difference between the two groups was statistically significant (P ＜ 0.001).The areas under the ROC curves of ADC and ADCR diagnosing neoplastic cysts were 0.94 ± 0.04,0.98 ± 0.02,respectively.An ADC of 3.105 × 10-3 mm2/s showed 81.3％ sensitivity and 94.4％ specificity for predicting neoplastic cysts.An ADCR of 1.525 showed 100％ sensitivity and 88.9％ specificity for predicting neoplastic cysts.Conclusions Diffusion-weighted imaging is of importance in the diagnosis and differential diagnosis of pancreatic cysts,and can be applied as a complementary tool for routine MRI.