There is currently no clinically valid biomarker for predicting the growth and prognosis of abdominal aortic aneurysms (AAA). The most promising candidates with highest diagnostic values are plasma D-dimers and markers of activated neutrophils, i.e. myeloperoxidase (MPO) or cell-free DNA. So far, case-control studies on these markers were almost exclusively performed by using healthy individuals for control. To validate the value of these markers in the clinical setting of a vascular surgery department, we analysed the diagnostic and prognostic potential of plasma D-dimers and MPO in 177 AAA patients versus 138 non-AAA patients with different vascular diseases. Significantly elevated levels of D-dimers were recorded for AAA patients compared with non-AAA patients, although the difference between the two groups was significantly smaller than in other studies comparing AAA patients with healthy controls. Surprisingly, MPO levels were significantly higher in non-AAA patients than in AAA patients. After adjusting for the confounding factors sex, peripheral artery disease (PAD) and internal carotid stenosis in multivariate regression models, neither D-dimers nor MPO remained independent correlates of AAA. In contrast, D-dimer plasma levels correlated well with the maximal aortic diameter. Combined analysis of D-dimers and circulating cell-free DNA levels derived from a previous study, failed to improve the predictive values for the maximal aortic diameter. In conclusion, our data show that D-dimers and MPO are no suitable biomarkers for monitoring AAA in a real-world setting of mixed vascular surgery patients.