Adiponectin is an adipose-derived plasma protein that demonstrates beneficial actions on myocardial injury under ischemic conditions. Circulating endothelial progenitor cells are reported to associate with rescue of cardiac damage after acute myocardial infarction (AMI). We examined whether circulating adiponectin level affects myocardial function and injury in patients with AMI. A total of 48 patients who underwent successful reperfusion treatment after AMI were enrolled. Cardiac function and perfusion defect were assessed by scintigraphic images of iodine-123 beta-methyl iodophenyl pentadecanoic acid in the acute phase and technetium-99m tetrofosmin in the long-term phase. Plasma adiponectin levels were measured by enzyme-linked immunosorbent assay at day 7 after AMI. Plasma adiponectin levels associated positively with myocardial salvage index representing the proportion of initial perfusion defect rescued by reperfusion and recovery of ejection fraction in the long-term phase and negatively with final infarct size. A positive correlation was also observed between adiponectin levels and number of circulating CD34(+) cells as determined by flow cytometry and between myocardial salvage index and recovery of ejection fraction independently associated with circulating CD34(+) cell levels. In conclusion, plasma adiponectin levels predict improvement of cardiac damage and function after reperfusion therapy in patients with AMI, suggesting that adiponectin could serve as a biomarker for assessment of myocardial injury after AMI.