A critical analysis of proteomes provides a basis for understanding the operation of complex biochemical systems. A personalized approach to therapy takes into account biological uniqueness of each patient at genome, transcriptome, and proteome levels, and is a priority area in molecular medicine. The identification of proteoforms, which have dramatic impact on the phenotype of a disease, is a fundamental task of personal molecular profiling. Considerable progress of proteomic approaches presented new avenues for accurate, specific, and high-performance protein analysis. Thus, the identification of new efficient bio-markers can be expected based on studies of aberrant proteoforms associated with various diseases.