Objective. To assess the relationship between hematological inflammatory signs, cardiovascular risk (CV) factors and prognosis in patients presenting with acute myocardial infarction (AMI) and coronary artery ectasia (CAE). Design. We investigated 3321 AMI patients who required urgent primary percutaneous intervention in two centres in the United Kingdom between January 2009 and August 2012. Thirty patients with CAE were compared with 60 age-and gender-matched controls. Blood was collected within 2 h of the onset of chest pain. CV risk factors were assessed from the records. Major acute cardiac events and/or mortality (MACE) over 2 years were documented. Results. CAE occurred in 2.7% and more often affected the right (RCA) (p = 0.001) and left circumflex artery (LCx) (0.0001). Culprit lesions were more frequently related to atherosclerosis in non-CAE patients (p = 0.001). Yet, CV risk factors failed to differentiate between the groups, except diabetes, which was less frequent in CAE (p = 0.02). CRP was higher in CAE (p = 0.006), whereas total leucocyte, neutrophil counts and neutrophil/lymphocyte ratio (N/L ratio) were lower (p = 0.002, 0.002 and 0.032, respectively) than among non-CAE. This also was the case in diffuse versus localised CAE (p = 0.02, 0.008 and 0.03, respectively). The MACE incidence did not differ between CAE and non-CAE (p = 0.083) patients, and clinical management and MACE were unrelated to the inflammatory markers. Conclusion. In AMI, patients with CAE commonly have aneurysmal changes in RCA and LCx, and their inflammatory responses differ from those with non-CAE. These differences did not have prognostic relevance, and do not suggest different management.