The aim of this study was to analyze the diagnostic accuracy of edema on T2-weighted (T2w) cardiac magnetic resonance imaging (CMR), presence of microvascular obstruction (MO) on first-pass enhancement (FPE) or on delayed enhancement (DE) CMR, and wall thinning on cine CMR to differentiate between acute (AMI) and chronic myocardial infarction (CMI) in patients with infarction on DE-CMR. Fifty patients were imaged 5 +/- 3 days (baseline) and 8 +/- 3 months (follow-up) after AMI at 1.5 T. Imaging findings were graded as present or absent in a blinded consensus reading. Edema was present at baseline in 48 (96%) patients and absent at follow-up in 49 (98%) patients. At baseline, MO was present in 29 (58%) patients on FPE-CMR and in 24 (48%) patients on DE-CMR (P = ns). At follow-up, persisting hypoenhancement was observed in ten (20%) patients on FPE-CMR, whereas two (4%) patients showed persisting hypoenhancement on DE-CMR (P<0.05). Wall thinning was present in 4 (8%) patients at baseline and in 20 (40%) patients at follow-up. Edema had high sensitivity (96%), specificity (98%), and accuracy (97%) to differentiate between AMI and CMI. Accuracy of all other imaging findings was lower compared to that of edema (P<0.001). In the presence of infarction on DE-CMR, T2w-CMR reliably differentiates between AMI and CMI.