Objective Left ventricular remodelling following a ST-segment elevated myocardial infarction (STEMI) is an adaptive response to maintain the cardiac output despite myocardial tissue loss. Limited studies have evaluated long term ventricular function using cardiac magnetic resonance imaging (CMR) after STEMI. Methods Study population consisted of 155 primary percutaneous coronary intervention treated first STEMI patients. CMR was performed at 4±2 days, 4 months and 24 months follow-up. Patients were treated with beta-blockers, ACE-inhibitors or AT-II-inhibitors, statins and dual antiplatelet according to current international guidelines. Results Mean left ventricular ejection fraction (LVEF) at baseline was 44%±8%. Twenty-one per cent of the study population had an increase of more than 5.0% after 4 months of follow-up and 21% of the cohort had a decrease of more than 5.0%. Patients with long-term LVEF deterioration have significantly larger end-systolic volumes than patients with improvement of LVEF (61±23 mL/m2 compared with 52±21 mL/m2, p=0.02) and less wall thickening in the remote zone. Patients with LVEF improvement had significantly greater improvement in wall thickening in the infarct areas and in the non-infarct or remote zone. Conclusion Contrary to previous studies, we demonstrate that myocardial remodelling after STEMI is a long-term process. Long-term LVEF deterioration is characterised by an increase in end-systolic volume and less wall thickening in the remote zones. Patients with LVEF improvement exhibit an increase in left ventricular wall thickening both in the infarct as well as in the remote zones.