OBJECTIVE: To compare a new semiquantitative visual scoring method with quantitative digital planimetry for determining left ventricular infarcted mass by use of cardiac delayed contrast-enhanced magnetic resonance imaging. METHOD: Seventy-seven patients with previous myocardial infarction underwent delayed contrast-enhanced magnetic resonance imaging using a 1.5T device for assessing myocardial viability and calculating the infarcted mass. Cine magnetic resonance imaging was used for assessing left ventricular function with the Simpson method. The infarcted mass was calculated on the delayed contrast-enhanced images according to the following 2 methods: planimetry and the scoring method. Simple linear regression and correlation and agreement between the methods and observers according to the Bland-Altman plot were used. RESULTS: The infarcted areas in all 77 patients were detected by use of cardiac delayed contrast-enhanced magnetic resonance imaging. The size of the infarction measured by planimetry was similar to that obtained with the scoring method, with a mean difference between measurements of only 1.03% of the left ventricular mass. Inter- (0.41%) and intraobserver (0.34%) variabilities indicated an excellent reproducibility of the scoring method. Infarcted mass showed a good correlation with ejection fraction and indexed end-diastolic and end-systolic volumes, r=-0.76, r=0.63, and r=0.67, respectively. CONCLUSION: In patients with previous myocardial infarction, delayed-enhanced magnetic resonance imaging provides accurate infarct size quantification by planimetry and by semiquantitative score.