Cardiovascular events pose significant morbidity and mortality burden to abdominal aortic aneurysm (AAA) patients. Arterial stiffness as measured by pulse wave velocity (PWV) is an independent predictor of cardiovascular risk. We investigated the relationship between aortic diameter and PWV. Consecutive patients with AAA were invited to participate. Patients completed a health questionnaire, received aortic ultrasound and carotid-femoral PWV (cfPWV) recordings with a Vicorder. Thirty patients were used for reproducibility assessment. A linear regression model was used to identify significant predictors of cfPWV. Observer variation was assessed using Bland and Altman analysis and the intraclass correlation coefficient. Three hundred and nine patients were included-148 with AAA and 161 controls. The mean difference for repeated cfPWV between observers was 0.11 ms(-1). cfPWV was positively correlated with age (r=0.24, P<0.001) and systolic blood pressure (r=0.29, P<0.001) and negatively correlated with aortic diameter (r=-0.15, P=0.008). There was no difference in cfPWV between AAA and control groups (9.75±2.3 ms(-1) vs. 9.55±2.3 ms(-1), P=0.43). Aortic diameter (P=0.003) and systolic blood pressure (P<0.001) were significant predictors of cfPWV independent of age, aspirin usage and a history of myocardial infarction. Patients with large AAA (>5 cm) had decreased cfPWV compared with patients with small AAA (P=0.02) or normal diameter aorta (P=0.02). Vicorder measurements of cfPWV are repeatable. cfPWV is negatively associated with infra-renal aortic diameter and reduced in large AAA. cfPWV is likely invalid for accurate arterial stiffness assessment in patients with AAA owing to the apparent confounding effect of aortic size.