In deep inferior epigastric perforator flap surgery, the amount of perfusion achievable in the contralateral side over a midline is unclear. Predicting contralateral perfusion preoperatively using computed tomographic angiography will allow efficient breast reconstruction with decreased complications. The authors used computed tomographic angiography to determine whether contralateral perfusion is related to blood vessel status across the midline. Preoperative computed tomographic angiography scans and intraoperative perfusion in patients who underwent breast reconstruction with a deep inferior epigastric perforator flap between January of 2018 and July of 2018 were checked prospectively. A vessel scoring system was prepared according to vessel density across the flap midline on the scan (grade 0, no visible vessels; grade 1, visible vessels with disconnection or could not be judged as grade 0 or 2; grade 2, definite vessels). Intraoperative flap perfusion was confirmed with indocyanine green angiography. Postoperative fat necrosis was analyzed using ultrasonography. Ninety-four patients were analyzed. Mean maximal contralateral perfusion length was as follows: grade 0, 7.50 ± 1.89 cm; grade 1, 7.93 ± 2.01 cm; and grade 2, 10.14 ± 2.29 cm. Grade 2 had a statistically significantly greater contralateral perfusion length than grade 0 (p < 0.001) and grade 1 (p < 0.001). Fat necrosis occurred in 27.3 percent (grade 0), 19.1 percent (grade 1), and 8 percent (grade 2), which was statistically significant (p = 0.035). A definite vessel connection across the midline (as in grade 2) in preoperative computed tomographic angiography indicates that contralateral perfusion will be sufficiently achieved. This vessel scoring system would be helpful in predicting flap perfusion and planning the surgery. Diagnostic, IV.