Disease processes are often associated with changes in tissue composition. For example, in atherosclerosis lipid and calcification are often found in the artery wall, whereas in healthy arteries the tissue microstructure is dominated by highly organized collagen. Such variations in composition likely result in changes in the material properties of the tissue. However, this relationship has not been fully investigated in atherosclerotic vessels. Using a combination of nanoindentation and spectroscopic techniques, our goal was to assess how changes in tissue composition affect the tissue's mechanical properties. Fourier Transform Infrared Spectroscopy (FTIR) was used to assess the biochemical composition of the tissue samples, such as the lipid and calcium content of fibrous tissues in diseased arteries. Nanoindentation was used to measure the local mechanical properties of the same tissue samples. This information was then correlated by position in the sample to assess the contributions of different constituents to the overall structure-property relations of these tissues.