The association between omega-3 (n-3 polyunsaturated fatty acids) and the clinical outcome of patients with cardiovascular diseases such as coronary heart disease is currently unclear, especially regarding its possible antiarrhythmic effects and the not quite understood mechanisms of action. In the last 15 years, several epidemiological studies have shown a lower incidence of sudden cardiac death with a diet rich in omega-3 or fish consumption. The antiarrhythmic properties related to omega-3 have been related to modulation of sodium-dependent ion channels or sodium-calcium exchangers of myocytes through a reduction of their excitability especially in ischaemic or damaged myocardial tissue. However, the results of experimental studies have not always been consistent. Although the role of omega-3 in preventing sudden cardiac death has been evaluated in several clinical trials that included patients with coronary artery disease (particularly in patients with post-myocardial infarction), the interpretation of such data must be treated with extreme caution. In particular, while a reduction in cardiac death was demonstrated by a meta-analysis of several randomized clinical trials, a reduced risk of sudden cardiac death has been described only in the GISSI-Prevenzione study, while in other studies the evidence that emerged is more controversial, with wide confidence intervals that support the possibility of heterogeneity in the distribution of the factors involved in the efficacy of treatment. Omega-3 is probably involved in the prevention of cardiovascular mortality through different mechanisms, and it is crucial to study its association with other drugs such as ACE inhibitors or calcium channel blockers. The study of antiarrhythmic drugs has been divided into prevention of supraventricular and ventricular arrhythmias. In these conditions, the role of omega-3 seems to be more pronounced in atrial tachyarrhythmias such as atrial fibrillation, but does not have a role in ventricular arrhythmias. In summary, the antiarrhythmic effect of omega-3 is not clearly evident and further studies are needed to investigate its beneficial effect in cardiac mortality compared with arrhythmic death.