We hypothesized that arterial stiffness is associated with changes in the arterial protein profile, particularly in relation to extracellular matrix (ECM) components, and aimed at determining differentially expressed proteins in human arterial tissue by quantitative proteome analysis in patients with different degrees of arterial stiffness. Arterial stiffness, assessed by carotid-femoral pulse wave velocity (PWV), central blood pressure and augmentation index by pulse wave analysis, as well as carotid intima-media thickness were measured the day prior to surgery in a group of patients undergoing coronary artery bypass grafting. Protein extracts of well-defined, homogenous, non-atherosclerotic individual samples of the left mammary artery from 10 of these patients with high PWV and 9 with low PWV, were compared by quantitative proteome analysis, using iTRAQ-labeling and nano-LC-MSMS. Of 504 quantified proteins, 28 were differentially expressed between groups with high and low PWV (p<0.05). Six out of eight members of the extracellular matrix family of small leucine-rich repeat proteoglycans displayed significant or borderline significant differences between the two groups (p<0.001, Fisher’s Exact Test). Only one other of 43 identified ECM proteins were differentially regulated (collagen alpha-1(VIII)). Several proteins related to smooth muscle cell function and structure were found in different amounts between the two groups. Changes in the arterial amounts of small proteoglycans, known to be involved in collagen fibrillogenesis, are associated with arterial stiffness. In addition, several proteins related to function of the human arterial smooth muscle are changed as well.