Cardiovascular diseases are the leading causes of morbidity and mortality worldwide, with the vast majority being coronary diseases and their consequences. The most common clinical presentations of coronary disease are acute coronary syndrome and stable angina pectoris, now referred to as chronic coronary syndrome under the new nomenclature. Despite advances in pharmacointerventional methods for treating coronary heart disease, the prevalence of ischemic heart disease is increasing, but overall mortality remains high. Risk factors for atherosclerotic disease have been known for decades; however, pharmacotherapy has not proven highly effective in modifying risk factors, particularly in cases of dyslipidemia. The aim of this research was to determine the level of endothelial lipase and examine the functional characteristics of high-density lipoproteins (HDL) in patients with acute and chronic coronary syndromes, and to compare these two groups. The study included 187 patients with acute coronary syndrome and 72 patients with stable coronary disease. The levels of endothelial lipase, cholesterol efflux, and the antioxidant capacity of HDL were statistically significantly higher in patients with chronic coronary syndrome (stable coronary artery disease). However, in this group of patients, the level of endothelial lipase did not correlate with the severity of coronary disease. In the group of patients who presented with acute coronary syndrome, the level of IL-6 and the anti-inflammatory capacity of HDL were significantly higher compared to those with stable coronary artery disease. Additionally, patients with acute coronary syndrome had more coronary artery segments affected by atherosclerosis. Endothelial lipase values ≤ 193,81 pg/mL, with test specificity of 93,1% and sensitivity of 37,4% in patients with chest pain, could be used as an exclusion criterion for establishing the diagnosis of acute coronary syndrome.