Sudden death during physical activity is sometimes the first manifestation of an underlying cardiovascular disease. Medical evaluations, including a resting 12-lead electrocardiogram, before and during physical training, enable the identification of still asymptomatic athletes with life-threatening heart diseases and help to protect them from sudden cardiac death. The incidence of sudden cardiac death is estimated at two cases for 100,000 young athletes per year, and it is 2–4 times higher when compared with non-athletes. The most common causes of sudden cardiac death in athletes younger than 35 are cardiomyopathies (e.g. familial hypertrophic cardiomyopathy in the U.S. and arrhythmogenic right ventricular cardiomyopathy in Italy, especially in the Veneto region). Hypertrophic cardiomyopathy is the most common genetic cardiovascular disease (1:500) caused by mutations in multiple genes, most of which encode sarcomeric proteins (especially beta-myosin heavy chain, cardiac myosin binding protein C and cardiac troponin T), and characterized by left ventricular hypertrophy (mainly interventricular septum). In contrast, arrhythmogenic right ventricular cardiomyopathy is a heart muscle disorder characterized by progressive replacement of the right ventricular myocardium with fatty and connective tissue. These two cardiomyopathies may lead to sudden death (predominantly during or after strenuous physical exercise) as a result of malignant dysrhythmias. The main aim of this article was to provide some information helpful in the recognition of electrocardiographic changes of inherited heart diseases that can cause sudden cardiac death in young physically active people, especially athletes.