Sudden cardiac death is one of the main causes of mortality in patients with structural heart disease. Although an implantable cardioverter defibrillator significantly reduces the mortality rate, many patients never receive a shock. Identification of high-risk patients would reduce the costs associated with this therapy and prevent the deleterious effect of inappropriate discharges. As scar tissue is the substrate of ventricular arrhythmias in patients with structural heart disease, scar characterization could allow stratification of the risk. The objective of this article is to review the role of scar characteristics in the pathogenesis of ventricular arrhythmias in patients with structural heart disease.