This study aimed to evaluate the potential associations of intermediate monocytes (CD14(++)CD16(+)) with myocardial remodelling in ST segment elevation myocardial infarction (STEMI) patients with diabetes.A total of 67 STEMI patients with diabetes were enrolled. The control group consisted of 65 STEMI patients without diabetes. All patients received emergency medical services for reperfusion therapy in less than 12 hours after onset of AMI. Blinded to patient clinical characteristics, monocyte subset analysis was performed using flow cytometry immediately after admission. mRNA of Chemokine Decoy Receptor D6 in each subset of monocytes was validated by Q-PCR. Expression of CCL2 in patient plasma was determined with an Elisa kit. Infarct size and left ventricular ejection fraction (LVEF) were measured using 3-dimensional echocardiography 3 days and 6 months after AMI. The incidences of recurrent cardiovascular events and death in each group were measured using the Kaplan-Meier estimator in follow-up during the next 24 months. Cox proportional-hazard models were further used to analyze the relationship of monocyte cell counts and event-free survival after adjusting for confounding factors.The number of circulating intermediate monocytes was significantly correlated with LVEF% and infarct size (r = -0.32; P = 0.008; r = 0.57, P < 0.001) in STEMI patients with diabetes compared with those without diabetes 6 months after AMI. Chemokine Decoy Receptor D6 transcript levels were lower in intermediate monocytes of STEMI patients with diabetes compared to the subsets in STEMI patients without diabetes (P < 0.001). Higher levels of CCL2 (pg/mL) were observed in STEMI patients with diabetes compared to STEMI patients without diabetes (P < 0.001). During a mean follow-up period of 24 ± 1 month, recurrent cardiovascular events or death occurred in 23 patients belonging to the STEMI with diabetes group and 10 belonging to the control group. Univariate Kaplan-Meier analysis revealed that counts of the intermediate monocytes according to median showed statistical significance in STEMI patients with diabetes (P = 0.010). After full adjustment for confounding factors, the cells were found to remain independently related to recurrent cardiovascular events or death in this group (P = 0.004, 95% CI: 1.62-12.49).Intermediate monocytes were associated with LV remodelling in STEMI patients with diabetes. The cells were predictive for recurrent cardiovascular events or death in these patients. A low level of D6 mRNA in the intermediate monocytes of STEMI patients with diabetes and high level of CCL2 in these patients may partially explain the causality.