Determination of the primary structure of proteins and peptides constitutes an important step in studying their properties. Currently, mass spectrometry is commonly applied to this end. The results of mass spectrometric measurements can be interpreted by means of either a database search or de novo sequencing methods. The appeal of the latter is due to their applicability to investigating unknown proteins, as well as the ones that cannot be analyzed with genomics or transcriptomics methods. In this paper, we briefly review the existing approaches to de novo sequencing of proteins and peptides, along with the problems that can be solved using those, and indicate directions and perspectives for their further development.