Depression affects about 40 % of people with coronary heart disease (CHD). This group with depression and CHD have increased mortality and morbidity, worse health-related quality of life, use health services more frequently and consequently cost the health service and the national economy considerably more than their non-depressed counterparts. A number of characteristics of depression and plausible mechanisms have been proposed to explain this observed association, which could lead to improved understanding of the association and lead to new interventions to improve cardiac outcomes. This review summarises the evidence linking depression with worse cardiac outcomes, considers specific aspects of depression which may predict worse outcomes and reviews the mechanisms that could potentially explain the direct or indirect association of depression with coronary outcomes.