BACKGROUND:  Perforator mapping with computed tomography angiography (CTA) prior to autologous breast reconstruction reduces donor-site morbidity and operative time, but is costly. The aim of this study was to evaluate whether pre-existing CT scans could be used for dominant perforator identification before autologous reconstruction. METHODS:  We identified all female patients who underwent mastectomy with immediate or delayed breast reconstruction with abdominal free flaps at a single institution between 2006 and 2016. Medical records were reviewed to identify patients with pre-existing CT scans of the abdomen/pelvis. CT images were reviewed by the senior surgeon and ranked on a 1 to 3 scale to indicate utility for preoperative planning. An analysis was performed to assess financial savings and radiation avoidance associated with the use of pre-existing scans. RESULTS:  Of 301 identified patients, 44.9% (n = 135) had an available pre-existing CT. A dominant perforator was identified on 92.6% of scans. A higher proportion of dominant perforators was identified using positron emission tomography (PET)/CT scans compared with CT scans with intravenous (IV) contrast and noncontrast CTs (p < 0.0001). Compared with PET/CTs and CTs with IV contrast, the average utility score for noncontrast CTs was lower (p = 0.0001). Dominant perforators were clearly identified in patients who had both a remote CT scan and a preoperative CTA. Perforator mapping using remote CT scans yielded a projected radiation reduction of 13.2 mGy per patient and yielded a projected annual U.S. health care savings of $28,459,638. CONCLUSION:  Our study suggests that pre-existing CT scans represent a viable and economical alternative for perforator mapping before abdominal-based free flap breast reconstruction.