Objective: To compare coronary flows between premature infants with and without hemodynamically significant patent ductus arteriosus (hsPDA) and to determine if coronary flow is influenced by medical PDA treatment. Design: Prospective, observational pilot study. Forty-three infants <32 weeks gestation underwent echocardiography when routinely indicated. Study group included infants with hsPDA requiring treatment. Comparison groups included infants with nonsignificant PDA and infants without PDA. Results: The study group (n = 13), compared with the comparison groups with nonsignificant PDA (n = 12) and without PDA (n = 18) had higher troponin levels (p = 0.003 and 0.004, respectively). In infants with hsPDA compared with infants with no PDA there was a significant increase in myocardial oxygen demand and decrease in left main coronary artery flow, with nonsignificant increase in cardiac output. Conclusions: Decrease in coronary artery flows and higher troponin values may suggest a “steal effect,” not allowing to meet the elevated myocardial oxygen demand in infants with hsPDA.