This study examines sociodemographic differences in myocardial infarction (MI) risk perceptions among people with coronary heart disease (CHD) (N = 3130). Two variables for comparative risk perceptions were computed: (1) own risk compared to that of an average person; and (2) own risk compared to that of an average person with CHD. Comparative optimism in MI risk perceptions was common, particularly among men and those with higher education. CHD severity and psychosocial resources mediated these sociodemographic differences. These results suggest challenges for secondary prevention in CHD, particularly regarding psychosocial interventions for communicating risk information and supporting lifestyle adjustments.