A total of 1492 outpatients with suspected coronary artery disease and who underwent computed tomography-derived fractional flow reserve analysis were examined. To investigate the effects of vessel morphology such as lumen diameter or volume on computed tomography-derived fractional flow reserve, nearly the same or subthreshold values affecting computed tomography-derived fractional flow reserve hemodynamics vessels were compared. Case 1 and 2 present almost the same vessel length (case 1 vs. case 2; 135.0 mm vs. 133.6 mm), low-attenuation plaque volume (0 mm3 vs. 0 mm3), intermediate attenuation plaque volume (12.5 mm3 vs. 35.5 mm3), and calcified plaque volume (4.7 mm3 vs. 0 mm3) in the right coronary artery. However, lumen volume (877.8 mm3 vs. 2443.7 mm3) and distal computed tomography-derived fractional flow reserve (0.79 vs. 0.96) were markedly different between the 2 patients. Computed tomography-derived fractional flow reserve depends not only on vessel length or plaque characteristics but also on lumen volume or vessel morphology.