Background Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital heart anomaly. We aimed to illustrate the clinical features and long-term prognosis of patients with ALCAPA.Methods Twenty three patients (13 males and 10 females, ages ranging from 2.5 months to 65 years) identified as ALCAPA in Beijing Anzhen Hospital from April 1984 to June 2009 were divided into two groups, based on the age of onset: group 1 (≤12 months, n=16) and group 2 (＞12 months, n=7).Results Fifty six point three percent of patients in group 1 had been misdiagnosed as endocardial fibroelastosis (9/16),18.8% as dilated cardiomyopathy (3/16) and 6.3% as myocardial infarction (1/16). Patients in group 2 were usually diagnosed as coronary heart disease, myocarditis, or patent ductus arteriosus. Electrocardiography in group 1 revealed abnormal Q waves with T wave inversion in leads I, avL, V4-V6, especially in lead avL (deep and wide Q wave); but no specific manifestations in group 2. A higher percentage of patients in group 1 had cardiomegaly on chest radiograph (86.7% vs. 33.3%, P=0.031), while pulmonary artery protrusion was more common in group 2 (26.7% vs. 83.3%,P=0.046). Lower left ventricular ejection fraction (LVEF) was present in group 1 than in group 2 ((48.5±11.5)% vs.(65.0±6.1)%, P ＜0.001). Apical ventricular aneurysm (62.5% vs. 0%, P=0.007), enhanced echogenicity of papillary muscles (87.5% vs. 28.6%, P=0.011) and endocardial thickening (93.8% vs. 14.3%, P ＜0.001) were more frequent in group 1 than in group 2. The ratio of the proximal right coronary artery (RCA) diameter to the aortic root diameter exceeded 0.14 in all cases, more prominent in group 2 (0.26±0.05 vs. 0.33±0.03, P=0.009). Increased coronary artery collaterals within the interventricular septum were detected in 18 patients (78.3%) by Doppler imaging. Twenty one patients underwent cardiac surgery, including left coronary artery (LCA) ligation (1/21), LCA ligation plus coronary artery bypass grafting (1/21), Takeuchi operation (7/21), and LCA reimplantation surgery (12/21). Four patients underwent concomitant mitral valve repair and one received mitral valve replacement. Aneurysm resection was performed in 3 cases. Six patients died in hospital after surgery, and the rest of the cohort had no overt symptoms during a follow-up period of 6 to 166 months. Their abnormal Q waves gradually regressed or disappeared, and the LVEF and left ventricle size returned to normal range with alleviation of mitral insufficiency.Conclusions The accurate diagnosis of ALCAPA can be made with serial diagnostic methods. ALCAPA can be successfully treated with several types of cardiac surgery, and surgeries of establishing two-coronary-artery circulation are the preferred operations nowadays, with good long-term prognosis.