Background: Plasma B-type natriuretic peptide (BNP) measured in acute coronary syndromes independently predicts mortality, myocardial infarction and congestive heart failure. Objectives: To investigate the relationship between the extent of delayed enhancement (DE) and microvascular obstruction (MO) in contrast-enhanced MRI and the plasma level of BNP in patients with acute myocardial infarction. Methods: The study group consisted of 41 consecutive patients (26 males, mean age 57 ± 11 years) with a first STEMI and complete reperfusion by primary PCI. EDTA-plasma samples were obtained 40 ± 15 h after admission and analyzed for NT-pro-BNP. Cardiac MRI (CMR) was performed 50 ± 29 h after coronary intervention on a 1.5 Tesla scanner. Cine images were acquired in contiguous short-axis views using a segmented steady-state free precession (SSFP) sequence (TR, 3 ms; TE, 1.5 ms; FA, 60°). Additionally, contrast-enhanced imaging was performed using a single shot steady-state free precession (IR-SSFP) sequence with an inversion recovery prepulse (TR, 2.4 ms; TE, 1.1 ms; FA, 50°; TI, 180 to 260 ms). Results: Strong correlations between NT-pro-BNT plasma levels and delayed enhancement extent (r = 0.74, p < 0.001) as well as MO (r = 0.7, p < 0.001) were observed. The correlation between LVEF and plasma levels of BNP, however, was only moderate (r = - 0.44, p = 0.002). In a multiple linear regression model, DE remains the only parameter with an independent linear association with BNP. Conclusion: NT-pro-BNP, a surrogate biomarker for prognosis after STEMI, is closely associated with myocardial damage as assessed by contrast-enhanced CMR.