Background. Aortic valve leaflets asymmetry has been known since Leonardo Da Vinci, but our aim was to evaluate their relationship between size and shape, not defined in children, which we hypothesized correlated with coronary arteries origin. Methods. Consecutive pediatric patients with trans-esophageal echocardiography (TEE), with or without trans-thoracic echocardiography (TTE), were included in our study. Exclusion criteria: a) bicuspid aortic valve, b) aortic valve stenosis, c) hypoplasia of aortic valve annulus, or aortic root; d) truncal valve, e) coronary artery atresia, f) previous surgery on aortic valve and/or coronary arteries. In pre-operative TTE and intra-operative TEE inter-commissural distance and length of aortic valve leaflets were measured in short axis view at the period of isovolumetric contraction in systole. Echocardiography investigations, anonymized and randomly coded, were independently reviewed by at least two readers. Echocardiography, angiography, cardiac CT scan and MRI, and operative notes were reviewed to identify origin of coronary arteries. Findings. 261 pediatric patients were identified, 93 excluded per our criteria, leaving 168 patients, age 2.6 ± 4.3 years, weight 12.87 ± 17.34 kg, 128 (76%) with normal and 40 (24%) with abnormal coronary arteries. In TTE and TEE measurements the non-coronary leaflet had larger area (P < 0.001), while the right and left had equal areas, but different shape, with the left leaflet longer (P < 0.001) and narrower (P = 0.005) than the right. With the major source of blood flow from the right coronary sinus, the non-coronary leaflet was still the longest. However, there was no statically significant difference between the size and shape previously observed between the right and left leaflets. Conclusions. Our study showed asymmetry of size and shape among aortic valve leaflets, and a correlation with coronary artery origin. The complex aortic root anatomy must be approximated to optimize function of any surgical repair. These findings also may prove useful in the pre-operative definition of coronary artery anatomy and in the recognition of coronary artery anomalies.