Glycans have important functions in many biological processes such as the interaction of cells with their extracellular environment to mediate cell adhesion, macromolecular interactions, and pathogen invasion. Glycomics comprises the analyses of glycans, released from proteins and/or lipids in any biological sample and is complementary to genomics, metabolomics and proteomics. This chapter highlights developments in glycobiomarker analysis as exemplified by two well-studied groups of disorders, the monogenic congenital disorders of glycosylation (CDG) and cancer. CDGs are a group of genetic defects with abnormal glycosylation of proteins and/or lipids. Protein-specific glycoprofiling has a couple of advantages over the more generally applied total serum glycomics. Glycomics is also a promising approach for personalized medicine in other disease settings and clinical applications beyond cancer and CDG. Protein-specific, high-resolution mass spectrometry of intact serum transferrin has significantly improved CDG diagnostics due to the robustness, speed and accuracy with which glycomarkers for CDG can be obtained for several genetic defects.