Molecular imaging of cancer metabolism in vivo is increasingly employed in clinical settings. Both 18F-FDG PET and hyperpolarized [1-13C]pyruvate MRSI are sensitive to glucose metabolism but differ in which part of the glycolytic pathway is probed. We hypothesize that hyperPET may improve cancer specific metabolic phenotyping. Simultaneous 18F-FDG PET and hyperpolarized [1-13C]pyruvate MRSI (hyperPET) was used in a pilot study, examining the metabolic characteristics exhibited by four different cancer cell lines in nude mice. The results indicated that the combined modalities may distinguish between cancer types.