Background: The approach (lateral thoracotomy versus median sternotomy) to repair coarctation of the aorta is frequently based on arch dimensions from the preoperative echocardiogram. Few studies have assessed the relationship between preoperative arch dimensions and late postoperative outcome. This study aimed to define how preoperative arch dimensions relate to late outcomes and identify long-term predictors of a successful operation. Methods: We performed a retrospective review of 102 neonates and infants undergoing isolated coarctation repair by lateral thoracotomy between 2003 and 2012. Long-term surgical success was defined based on the following five factors: corrected arch gradient below 20 mm Hg, blood pressure cuff gradient below 15 mm Hg, systolic blood pressure below the 95th percentile during the clinic visit, no antihypertensive medication use, and freedom from reintervention. Regression analysis was performed to identify factors that would predict the need for reintervention and long-term success. Results: At a median of 6 years of follow-up, long-term success was achieved in 63% (56 of 89) of patients, and 94% (96 of 102) were free of reintervention. Bivariate analysis showed that patients requiring reintervention had smaller absolute isthmus dimension (p = 0.04). No significant predictors for reintervention or long-term success could be identified, although a larger distal transverse arch dimension may play a role in long-term success (hazard ratio, 0.7; 95% confidence interval, 0.05 to 1.0; p = 0.06). Conclusions: Aortic arches of various dimensions were successfully repaired by lateral thoracotomy. No significant predictors for reintervention or long-term success could be identified, although the distal transverse arch dimension may play a role in long-term success.