The GISSI-Prevenzione trial established the efficacy of n-3 polyunsaturated fatty acids (PUFAs) for reducing mortality in patients after recent myocardial infarction. The generalisability of such results to clinical practice could vary according to other individual patient characteristics. We analysed the GISSI-Prevenzione database to assess whether other major risk factors, comorbidities, dietary habits, or medications could interact with the efficacy of n-3 PUFA treatment to reduce total mortality. We found no evidence that concomitant disease states, habits, or interventions altered the therapeutic benefit of n-3 PUFA consumption in survivors of recent myocardial infarction.