Hazelnuts (Corylus avellana L.) are rich in fats, protein, valuable fibre content, phytonutrients and antioxidants such as vitamin E. The health benefits of hazelnut consumption arise from the synergic action of unsaturated fat or bioactive compounds including plant sterols and dietary fibre. After introducing the key nutritional features of hazelnuts, the chapter describes advances in metabolomics and outlines the results of epidemiological and clinical studies on both healthy and unhealthy volunteers. The chapter considers molecular studies of both nutrigenomics and nutri-epigenomics before looking ahead to future trends in this area of research.