Abstract： Objective To study the water/fat ratio of patients with pancreatic ductal adenocarcinoma (PDAC) and mass-forming focal chronic pancreatitis (MFP),and to provided guide for the clinicians.Methods Thirteen patients with PDAC,8 patients with MFP and 20 healthy volunteers were scanned by GE 3.0T MR IDEAL sequence.The signal strength of outcome images was measured; the water/fat ratio analysis was performed.Two kinds of formula were applied,the first was WF1 =SW/SF,the second was WF2 =( SIP + SOP) / ( SIP - SOP).SW was the signal strength of water,SF was the signal strength of fat,and SIP was the signal strength of in-phase,while SOP was the signal strength of opposite phase.Results By using the WF1 formula,the water/fat ratio of normal pancreas,PDAC,MFP was 7.97 ±0.95,9.94 ±1.19,5.08 ±0.49,respectively.By using the WF2 formula,the water/fat ratio of normal pancreas,PDAC,MFP was 11.51 ± 1.62,13.87 ±1.84,5.73 ±0.65,respectively.The difference among the three groups was statistically significant (P ＜ 0.05 ) under the same formula.The value of WF2 was higher than that of WF1,the difference in PDAC groups was also statistically significant ( P ＜0.05 ).Conclusions The water/fat ratio of pancreas among PDAC,MFP and normal pancreas is different.PDAC has the highest water/fat ratio,followed by the normal pancreas; MFP has the lowest ratio.