To identify multi-detector computed tomographic (MDCT) features discriminating bicuspid aortic valves (BAVs) from tricuspid aortic valves (TAVs) in patients with aortic valvular disease using surgical findings as reference. Forty-five patients underwent ECG-gated cardiac MDCT scans prior to aortic valve replacement. Morphologic patterns of aortic valves on MDCT were classified into: bicuspid without raphe (A), fused valve with a fish-mouth opening (B), fused valve without a fish-mouth opening (C), and tricuspid without fusion (D). To differentiate congenital raphe of BAV from commissural fusion of TAV, MDCT features of patterns B and C were evaluated. Diameters of the aortic root and ascending aorta between patients with BAVs and TAVs were also compared. Patterns A (n = 6) and B (n  = 6) were all bicuspid, in pattern C: 8 of 26 (30.8%) were bicuspid, and pattern D (n  = 7) were all tricuspid. In patterns B and C, uneven cusp size, round-shaped opening and midline calcification at leaflet fusion were strongly associated with BAVs (all, P < 0.05). The mean length of leaflet fusion in BAVs was significantly larger than in TAVs (13.5 vs. 8.7 mm, P < 0.0001), with a cutoff value of 10.3 mm providing a sensitivity of 85.7%, a specificity of 83.3%, and an area under the ROC curve of 0.90. In all patients, the mean diameter of the ascending aorta was larger in patients with BAVs than with TAVs (43.3 vs. 39.7 mm, P < 0.05). MDCT features of uneven cusp size, round-shaped opening, midline calcification, longer leaflet fusion and larger diameter of the ascending aorta can be helpful in distinguishing BAVs from TAVs.