In countries like the Netherlands, patients surviving a myocardial infarction (MI) form a growing part of the population. This thesis evaluates how types of unsaturated fatty acids in the diet and their blood biomarkers are related to diabetes and long-term mortality risk after MI. Most studies were done in the Alpha Omega Cohort of 4837 post-MI patients. Higher intakes and blood levels of omega-3 fatty acids from fish were associated with a 30% lower risk of fatal coronary heart disease. A low blood level of linoleic acid predicted type 2 diabetes, although the utility of this biomarker in clinical practice is not yet clear. Odd-chain fatty acids in the blood, which reflect dairy intake, were affected by dietary fiber intake in post-MI patients. This may explain favourable associations with diabetes reported in the literature. This thesis provides important evidence for dietary guidelines for patients with coronary heart disease.