Background. Carotid artery stenosis, especially hemodynamically significant, is a major risk factor for ischemic stroke. While symptomatic carotid stenosis (SCS) clearly requires surgical intervention, the treatment of asymptomatic carotid stenosis (ACS) remains controversial. Current guidelines emphasize the importance of identifying unstable or “vulnerable” plaques prone to rupture and subsequent thromboembolic complications. Objective. The aim of this study was to investigate morphological and biochemical differences between stable and unstable atherosclerotic plaques in patients with SCS and ACS, paying special attention to the role of extracellular matrix (ECM) components, glycocalyx molecules, and matrix metalloproteinases (MMPs) in plaque destabilization. Patients and methods. The study enrolled a total of 28 patients who underwent carotid endarterectomy. They were divided into symptomatic (n=11) and asymptomatic (n=17) groups. Plaque samples were obtained intraoperatively and analyzed using histopathological and biochemical methods. Morphological assessment included the presence of neovascularization, inflammation, and the integrity of the fibrous cap. Biochemical analysis focused on the expression of ECM components (versican, syndecan, decorin) and MMP activity (MMP-1, MMP-2, MMP-9, MMP-12) using Western blotting and zymography. Preoperative ultrasound was used to evaluate plaques based on their echogenicity and structural features. Statistical analysis was performed to compare plaque characteristics between groups and identify correlations between ECM components and MMP activity. Results. Unstable plaques, regardless of the presence of symptoms, exhibited neovascularization and a significant decrease in the levels of syndecan and decorin (p