PURPOSE: The free deep inferior epigastric artery perforator (DIEP) flap is a popular option for autologous breast reconstruction. However, the anatomy of the deep inferior epigastric artery(DIEA) may vary from one individual to another. Unexpected vascular anomaly can confuse the surgeon and affects on the safety of the free DIEP flap. MATERIALS AND METHODS: Thirty five consecutive patients who underwent free DIEP/TRAM flap for immediate breast reconstruction between Mar. 2010 and Oct. 2010 were enrolled in this study. Computed tomography angiography (CT angiography) of abdomen was evaluated part of our standard preoperative assessment: atypical patterns of DIEA/DIEP were evaluated by preoperative CT angiography and compared with intraoperative finding. RESULTS: Atypical patterns of DIEA/DIEP which may affect preoperative planning were noted as the following: Circummusclar/subfascial DIEA (n=1), DIEA running underneath rectus muscle (n=8), septocutaneous perforator (n=3), peritoneo-cutaneous perforator (n=1), a large branch going into peritoneum (n=1), and very early division and muscle penetration of DIEA (n=1). CONCLUSION: Atypical DIEA/DIEP that might change the operation plan is not rare, so the individualized planning based on the preoperative CT angiography is recommended. Preoperative CT angiography could help to select reliable and easy-to-dissect perforator in free DIEP/TRAM breast reconstruction.