The aim of this study was to prospectively investigate the clinical characteristics including symptoms and long-term mortality in patients with acute myocardial infarction (AMI) accidentally admitted to non-cardiology departments (NCDs). For comparison, similar observations in patients admitted to the coronary care unit (CCU) were collected. During a 1-year period, consecutive patients having cardiac troponin I measured at the Odense University Hospital were considered. The hospital has 27 clinical departments. Patients were classified as having an AMI if the diagnostic criteria of the universal definition were met. Follow-up was at least 1 year with mortality as the clinical end point. Of 3,762 consecutive patients, an AMI was diagnosed in 479, of whom 114 patients (24%) were hospitalized in NCDs and 365 (76%) in the CCU. Chest pain or chest discomfort more frequently occurred in patients from the CCU (83%) than in patients from the NCDs (45%, p <0.0001). At median follow-up of 2.1 years, 150 patients had died: 73 (64%) of patients from the NCDs and 77 (21%) of the patients from the CCU. In the multivariable Cox regression analysis, the adjusted hazard ratio of mortality for patients from the NCDs versus CCU was 2.0 (95% confidence interval 1.3 to 3.2). In conclusion, chest pain/discomfort was absent in more than half of the patients with AMI admitted to NCDs, and admission to NCDs was an independent predictor of a 2 times higher long-term mortality in comparison with admission to the CCU.