Ischemia-modified albumin (IMA) is a laboratory biomarker of cardiac ischemia. Our study aims to determine whether IMA can estimate or represent to any degree the extent of myocardial ischemia. We expect that the higher the marker of cardiac necrosis (maximum value after serial measurements) the greater the preceding cardiac ischemia, indicated by IMA in patients diagnosed with STEMI prior to direct percutaneous coronary intervention (PCI). We studied 216 patients indicated for direct PCI with a diagnosis of ST elevation myocardial infarction. Biochemical analysis of IMA was carried out using the albumin cobalt binding (ACB®) test. We also obtained relevant values for markers of myocardial necrosis (CK, CK-MB, cTnT). In all patients, there was an increased level of IMA prior to the procedure (116 ± 16.9 kU/l); also raised were levels of CK (17.32 μkat/l), CK-MB (4.85 μkat/l) and cTnT (2.97 μg/l) taken as the maximum values obtained after serial measurements at 12, 18, and 24 h after the procedure. We observed that there was no significant association between increase in IMA and cTnT (R2 = 0.0068, p = 0.483). This was also the case for CK-MB (R2 = 0.0011, p = 0.637). IMA does not estimate the extent of ischemia in patients with ST elevation myocardial infarction. However, its absence can be used qualitatively to rule out cardiac ischemia.