The clinical assessment of human brain tumors requires the use of non-invasive information measurement technologies, usually from the modalities of imaging or spectroscopy. The latter may provide insight into the tumor metabolism. The Magnetic Resonance Spectroscopy (MRS) signal is the result of the combination of heterogeneous signal sources. In this study, we investigate the use of two spectral decomposition techniques for the identification of such sources in MRS from brain tumors collected in an international database, and for a number of different diagnostic problems.