High-sensitive Troponin I (hsTnI) facilitates the early diagnosis of myocardial infarction (MI). However, since hsTnI has not been well characterized in non-ischemic cardiac conditions, the predictive value of hsTnI for MI remains unclear.hsTnI (ADVIA Centaur, Siemens) on admission was analyzed in 929 patients with acute cardiac condition and invasive ascertainment of coronary status by catheterization.Hs-TnI upon presentation was higher in patients with STEMI (median 1.27ng/mL, IQR 0.13–14.5ng/mL) as compared to patients with Non-STEMI (0.66ng/mL, IQR 0.10–4.0ng/mL, p<0.001) whereas it did not differ from STEMI in Tako-Tsubo cardiomyopathy (2.57ng/mL, IQR 0.17–8.4ng/mL) and myocarditis (9.76ng/mL, IQR 2.0–27.0ng/mL). In patients with resuscitation of non-ischemic cause (0.31ng/mL, IQR 0.06–1.3ng/mL), acute heart failure (0.088ng/mL, IQR 0.035–0.30ng/mL) and hypertensive emergency (0.066ng/mL, IQR 0.032–0.34ng/mL), hs-TnI was elevated above the recommended threshold of 0.04ng/mL. At this cutpoint of 0.04ng/mL, hsTnI indicated acute MI (STEMI or Non-STEMI) with a sensitivity of 88% and a specificity of 45% (ROC–AUC 0.748). When patients with STEMI were excluded, hsTnI indicated Non-STEMI with a sensitivity of 87% and a specificity of 45% (ROC–AUC 0.725). When sequential measurements were taken into account in a restricted cohort, a maximum hsTnI of ≥0.40ng/mL provided a sensitivity of 89% and a specificity of 85% (ROC–AUC 0.909) for Non-STEMI.HsTnI is a sensitive, albeit unspecific marker of MI. In patients with mildly elevated hsTnI and without evidence for STEMI, we suggest serial assessment of hsTnI and a 10-fold higher cutpoint of 0.40ng/mL before Non-STEMI is assumed.