OBJECTIVES: The objectives of this study were to identify interrelations between matrix metalloproteinase-2 (MMP2)/MMP9 levels and clinical variables in patients with aortic root/ascending aortic aneurysms and to describe comorbidities as possible biasing factors in the widely discussed correlation of serum MMP levels and aortic diameter. METHODS: Serum MMP9 and MMP2 levels were quantified in 32 consecutive patients with ascending aortic and/or aortic root aneurysms (>45 mm) at the Heart Center University of Freiburg from May 2013 to January 2014. The influence of comorbidities and medication on serum MMP2 and MMP9 levels was studied. We took into account ascending aortic diameter (aAD), aortic valve configuration, hypertension, age and hyperlipidaemia as factors possibly altering serum MMP levels. The relation between serum MMP levels and aAD was examined by a correlation test based on ranks. RESULTS: Serum MMP2 levels and aAD correlated positively. Correlation was increased in patients without hyperlipidaemia (Spearman's rho = 0.62, P = 0.008 in patients without hyperlipidaemia;rho = 0.409, P = 0.020 in all patients). Serum MMP9 levels did not correlate with aAD and showed greater variation. Serum MMP9 levels were significantly associated with hyperlipidaemia (P = 0.037). CONCLUSIONS: The distinct correlation patterns in patients with and without hyperlipidaemia have to be considered when defining the potential of MMP2 as a biomarker in future studies. The relation between MMP9 and hyperlipidaemia has to be further investigated.