Background: CT angiography has become the gold-standard for pre-operative planning prior to DIEP flap reconstructions. Recent studies have shown a high sensitivity and specificity and significant reductions in operative time. Importantly, previous studies have documented excellent correlation between CTA and operative perforator location, but not their clinical significance. This study seeks to specifically evaluate the clinical utility of CTA in DIEP free flaps. Methods: This study includes 47 sequential DIEP free flap breast reconstruction cases in 34 patients. Pre-operative CTA of the deep inferior epigastric system was obtained with up to three dominant perforators marked by radiologist on 3-D skin-level reconstruction. Each scan was reviewed pre-operatively by the surgeon, and planned perforators were documented. Post-operatively, the perforators used were documented. Results: Surgeons planned to use at least one marked perforator in 45/47 cases (96%). In 17/47 cases (36%) surgeons used perforators exactly as planned. In 34/47 cases (72%) perforators were used as planned with or without the addition of one or more extra perforators. In 19/47 cases (40%) at least one perforator was used that was neither marked by the radiologist nor surgeon pre-operatively. The most common reason (six cases) for the addition of perforators was, “additional perforator(s) easy to add” followed by “planned perforator(s) insufficient” (five cases). In 6/47 cases (13%) completely different perforators were used than that which were planned; in all cases the perforator(s) planned and ultimately used were amongst those marked by radiology. In three cases, “larger/better perforator(s) found,” in two “planned perforator contained only vein,” and in one “perforator with less complicated intramuscular course found.” Conclusion: There is no doubt that CTA mapping of perforators prior to DIEP flap surgery increases surgeon confidence and reduces operative time; however, this study shows that there are still a significant number of changes made based on clinical judgment. Over two-thirds of the time, variations are made from the pre-operative plan, usually with the addition of one or more perforators oftentimes not appreciated on CTA. But notably, over one in ten perforator plans is changed completely based on intraoperative findings. This study highlights the importance of surgeon review of CTA images. Caution is warranted in reliance on CTA mapping, and significant perforators should not be sacrificed until the anticipated perforator(s) have been exposed and evaluated.