This review discusses the application of spectroscopic methods for the structural analysis of chitin and chitosan. Chitin, the second most abundant natural polymer, and its deacetylated derivative chitosan, are versatile biopolymers with a wide range of applications in medicine, agriculture, and the food industry. These polymers have unique chemical, physicochemical, and biological properties, and their structures can vary depending on the source and production conditions. Spectroscopic techniques are essential for fully characterizing chitin, chitosan, and their derivatives. The review focuses on the use of spectroscopic methods, including X-ray spectroscopy, infrared (IR) spectroscopy, UV-Vis spectroscopy, mass spectrometry (MS), and nuclear magnetic resonance (NMR), for structural and physicochemical analysis of chitin and chitosan. X-ray spectroscopy provides information on the electronic and geometric structures of these compounds, while IR spectroscopy is used to identify functional groups and determine the degree of deacetylation. The review also highlights the importance of these techniques in understanding the structural differences between chitin and chitosan, as well as their polymorphic forms. X-ray diffraction is used to determine the crystallinity and structure of chitin and chitosan, while IR spectroscopy helps identify the presence of specific functional groups and the degree of deacetylation. The review discusses the differences in the physicochemical properties of chitin and chitosan, including their solubility, crystallinity, and reactivity. These properties are influenced by factors such as the degree of N-acetylation, molecular weight, and the source of the material. The review also covers the use of X-ray and IR spectroscopy in the analysis of chitosan derivatives, including salts and cross-linked forms. These techniques are essential for understanding the structural and functional properties of chitin and chitosan, which are important for their applications in various industries. Overall, the review emphasizes the importance of spectroscopic methods in the structural analysis and characterization of chitin and chitosan.This review discusses the application of spectroscopic methods for the structural analysis of chitin and chitosan. Chitin, the second most abundant natural polymer, and its deacetylated derivative chitosan, are versatile biopolymers with a wide range of applications in medicine, agriculture, and the food industry. These polymers have unique chemical, physicochemical, and biological properties, and their structures can vary depending on the source and production conditions. Spectroscopic techniques are essential for fully characterizing chitin, chitosan, and their derivatives. The review focuses on the use of spectroscopic methods, including X-ray spectroscopy, infrared (IR) spectroscopy, UV-Vis spectroscopy, mass spectrometry (MS), and nuclear magnetic resonance (NMR), for structural and physicochemical analysis of chitin and chitosan. X-ray spectroscopy provides information on the electronic and geometric structures of these compounds, while IR spectroscopy is used to identify functional groups and determine the degree of deacetylation. The review also highlights the importance of these techniques in understanding the structural differences between chitin and chitosan, as well as their polymorphic forms. X-ray diffraction is used to determine the crystallinity and structure of chitin and chitosan, while IR spectroscopy helps identify the presence of specific functional groups and the degree of deacetylation. The review discusses the differences in the physicochemical properties of chitin and chitosan, including their solubility, crystallinity, and reactivity. These properties are influenced by factors such as the degree of N-acetylation, molecular weight, and the source of the material. The review also covers the use of X-ray and IR spectroscopy in the analysis of chitosan derivatives, including salts and cross-linked forms. These techniques are essential for understanding the structural and functional properties of chitin and chitosan, which are important for their applications in various industries. Overall, the review emphasizes the importance of spectroscopic methods in the structural analysis and characterization of chitin and chitosan.