Sudden cardiac death is one of the main causes of death in Western countries. Identification of possible causes and their intrinsic mechanisms, is directed to achieve a better risk stratification, which permits the obtention of a more effective primary and secondary prevention. In the last two decades, important advances in the field of arrhythmia treatment have been obtained, which could have an important impact on the incidence of sudden death in the highest risk groups. However, the low positive predictive value of the diagnostic tools available nowadays, as well as the high number of patients who have sudden death as the first initial symptom of their disease, represent an important limitation for the primary prevention on the whole of the general population. In this article we review different diseases associated with sudden death, with special focus on the subgroup of patients with higher risk within each disease group, as well as the problems in establishing an accurate definition of sudden death.