Among patients with acute coronary syndrome, diabetes mellitus in particular is a marker of poor clinical prognosis. Diabetics tend to have rapid progression of atherosclerosis, leading to an increased rate of multi vessel disease, which commonly requires recurrent revascularization. According to the current European Society of Cardiology (ESC) guidelines on myocardial revascularization, coronary artery bypass grafting (CABG) is preferred over percutaneous coronary intervention in diabetic patients. This recommendation is strictly related to a higher rate of short- and long-term adverse cardiovascular outcomes demonstrated after PCI. However, due to the aging and numerous comorbidities, PCI often remains the only available revascularization option. Many factors are postulated to play a role in the pathophysiological background of unfavourable results. Chronic vascular inflammation, endothelial dysfunction with increased oxidative stress, and increased platelet activation are cardiovascular responses to hyperglycaemia. In addition, these chronic inflammatory responses are often exacerbated by the drug eluting stent which can lead to delayed endothelialisation of stent and subsequently impaired vascular healing process.