Multivessel disease (MVD) is a significant risk factor in patients with acute ST-segment elevation myocardial infarction (STEMI). Whether the presence of chronic total occlusion (CTO) poses an additional hazard is still unknown. The objective of this study was to evaluate the impact of CTO on survival in STEMI patients. The study group consisted of 836 STEMI patients treated with primary percutaneous coro-nary intervention (PCI). MVD was diagnosed in 52.3%, and CTO in 17.5% of patients. In MVD patients, 30-day mortality was 4.8% (6.8% in the CTO and 3.8% in the non-CTO group, p = 0.167). After 6 years, of the 437 patients with MVD, 56 (38.6%) died in the CTO group, and 74 (25.4%) in the non-CTO group (p = 0.0055). CTO was an independent predictor of long-term mortality (OR 2.07, 95% CI 1.30-3.28, p = 0.002), whereas triple vessel disease was not (OR 1.27, 95% CI 0.78-1.97, p = 0.358). The other independent predictors of mortality were: age, anterior myocardial infarction, and PCI failure. The presence of CTO is an independent predictor of the long-term mortality in STEMI patients treated with primary PCI. (Cardiol J 2017; 24, 2: 117-124).