Ventricular dysfunction in patients after Fontan-like operations (FLOs) is a serious complication that might contribute to poor long-term results. Ischemic heart disease will have debilitating consequences on a Fontan heart. Ten patients (15.8 ± 5.01 years) after FLO had transesophageal echocardiography and cardiac catheterization 9.3 ± 4.2 years after surgery. Myocardial perfusion was assessed by NH₃-positron emission tomography (rest/adenosine) and compared with that of 10 healthy adults (26.1 ± 6.3 years). Ventricular function was normal in 4 and reduced in 6 patients; end systolic and end diastolic meridional wall stress was significantly elevated in the FLO group. Coronary angiography revealed no stenosis of the coronaries. Compared to normals, myocardial blood flow (MBF) at rest was higher in the FLO group (0.99 ± 0.25 vs 0.77 ± 0.17 ml/g/min, p < 0.05), whereas MBF after vasodilatation (2.12 ± 0.78 vs 3.10 ± 0.85 ml/g/min, p < 0.05) and coronary flow reserve (CFR) was reduced (2.5 ± 0.88 vs 4.1 ± 1.01, p < 0.05), especially in those with impaired ventricular function. Coronary vascular resistance after vasodilatation was elevated in the FLO group (38.2 ± 17.4 vs 24.5 ± 8.3 mmHg/ml/g/min, p < 0.05). Altered MBF, increased meridional wall stress, and impaired CFR are common findings in FLO. Attenuated CFR and reduced ventricular function are significantly correlated and may be risk factors for the long-term outcome.