This study investigates structural cerebellar correlates of executive function in adolescents and young adults (AYAs) with congenital heart disease (CHD). The sample includes 22 AYAs with CHD and 22 matched healthy controls. There were significant cerebellar volume differences between CHD patients and controls and CHD patients performed significantly more poorly on several measures of executive function (EF). Furthermore, we found a significant single dissociation such that EF measures were related to the posterior CB but not the anterior, lending support to previously established CB theories. We demonstrate that the posterior CB contributes to some aspects of EF above and beyond processing speed alone, suggesting a unique contribution that warrants further study. Exploratory analyses are discussed as well. A better understanding of these cognitive outcomes in CHD will allow us to identify patients at risk of poor functioning and to better understand the role of the CB in higher-order cognition.