Abstract： Objective To investigate the CT spectral imaging features of pancreatic serous oligocystic adenoma and mucinous cystic neoplasms and to assess the value of spectral CT in differentiating between pancreatic serous oligocystic adenoma and mucinous cystic neoplasms. Methods From Feb.2010 to Dec. 2010, 27 patients with cystic neoplasms of the pancreas (group one with 15 serous oligocystic adenomas and group two with 12 mucinous cystic neoplasms) underwent dual-phase CT spectral imaging followed by surgery. Quantitative values (age, tumor size, CT value change as function of photon energy,effective-Z, iodine-water concentration, and calcium-water concentration) were compared with independent samples t test and Mann-Whitney test and non-quantitative parameters (gender, symptom, and tumor location) were compared with Chi-square test (Fisher exact). The parameters with significant differences between two groups were analyzed further and the performance of multiple parameters for joint differential diagnosis was evaluated with discriminant analysis. Results Compared to patients with mucinous cystic neoplasms, patients with serous oligocystic adenoma had younger age, lower frequency of being symptomatic and smaller tumor size. The CT values on 40 keV to 60 keV( with 10 keV increment) in late arterial phase [(36±13)HU vs. (62±23)HU, (26 ±8)HU vs. (40±15)HU, and (19±6)HU vs. (27±10)HU respectively] and 40 keV to 50 keV (with 10 keV increment) in portal venous phase [ (43 ± 14 )HU vs.(61 ±25)HU and (30 -10)HU vs. (40 ± 16)HU respectively], effective-Z (late arterial phase 7.80 ± 0. 16 vs. 8.05 ± 0. 21, and portal venous phase 7. 87 ± 0. 15 vs 8.02 ± 0. 22 ), concentration of calcium (water) [late arterial phase (5 ±3) g/L vs. (11 ±4) g/L, t= -3.836, P=0.001 and portal venous phase (7 ± 3 ) g/L vs. ( 10 ± 5 ) g/L, t = - 2.071, P = 0. 049 ] and iodine (water) [ late arterial phase (0.38 ±0.24) g/L vs. (0.78 ±0.32) g/L, t = -3.755, P=0.001 and portal venous phase (0.48 ± 0. 24) g/L vs. (0. 72 ± 0. 34 ) g/L, t = - 2. 161, P = 0. 041 ] were lower in serous oligocystic adenoma than those in mucinous cystic neoplasms. In discriminant analysis, multiple parameters [ age, symptom,tumor size, CT values on 40 keV to 50 keV, effective-Z, concentration of iodine (water) in late arterial phase and concentration of calcium (water) in portal venous phase] showed high accuracy (100%, 27/27 )of joint diagnosis between serous oligocystic adenoma (100%, 15/15 ) and mucinous cystic neoplasms (100%, 12/12). Conclusions The serous oligocystic adenoma and mucinous cystic neoplasms had distinct characteristic findings on CT spectral imaging. CT spectral imaging is highly accurate in the differential diagnosis between serous oligocystic adenoma and mucinous cystic neoplasms.