AIMS: This study aimed to assess how diabetes influences the quality of care and longer-term outcomes in contemporary STEMI cohorts. METHODS: We analysed 283,658 adults hospitalised with STEMI from the United Kingdom Myocardial Ischaemia National Audit Project (MINAP) registry between 2005 and 2019. This was linked with Office of National Statistics data to provide out of hospital mortality outcomes. We compared longer-term outcomes depending on diabetes status and assessed the effect of quality of care using the opportunity-based quality-indicator score (OBQI). RESULTS: Individuals with diabetes were older (median age 68.7 vs. 65.5), underwent percutaneous coronary intervention less frequently (60 % vs. 63 %) and were less likely to achieve a door-to-balloon time of <
60 min (69 % vs. 75 %) or <
120 min (89 % vs. 92 %). Their adjusted all-cause mortality risk was higher during follow-up, from 30 days (HR: 1.49, CI: 1.44-1.54), to up to 10 years of follow up (HR: 1.54, CI: 1.52-1.57), compared to individuals without diabetes. Excellent inpatient care was associated with lower mortality rates within individuals with diabetes (Diabetes: HR 0.56, CI: 0.50-0.64, No diabetes: HR 0.62, CI: 0.58-0.67). CONCLUSIONS: Individuals with diabetes have a higher risk of long-term mortality after STEMI. They experience delays in angiography and receive lower quality inpatient care.