Pre-Fontan cardiac assessment with CMR in conjunction with cardiac catheterization has increasingly become the standard of care. Cardiac catheterization and CMR performed for pre-Fontan assessment at a single institution between April 2017 and June 2020 were analyzed. Our cohort consisted of 43 patients with median age of 3.7 years(range 1.8-14) at the time of CMR. Median age at Fontan operation was 4 years (2.4-14). We found significant correlation between CMR derived ventricular end diastolic, end systolic volume, ejection fraction and cardiac catheterization derived ventricular end-diastolic and mean superior vena cava pressure, and duration of post-operative hospital stay after Fontan operation.