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N-doped carbon nanotubes (N-CNTs) can be described as a 1D quasi-molecules with unique electrophysical and surface properties, which make them a promising material for different applications. Incorporation of nitrogen in sp2-carbon layers accelerates electron transfer, provides protonation of nitrogen and induction of the negative charge on the adjacent carbon atoms that increases electron capacity and makes N-CNTs an excellent material for energy storage applications and catalysis. Physical and chemical properties of N-CNTs depend on the type and content of nitrogen atoms incorporated in their structure. In some cases, oxidative treatment is crucial for tuning the structure and hydrophilic behavior of N-CNTs. Particularly, the presence of carboxylic, anhydride, lactone and phenol groups induces the acid behavior of the carbon surface whereas carbonyls lead to the base properties. At the same time acid groups promote fine dispersion of metal particles on CNT surface, that is important for catalytic properties. Mechanisms of the oxidation and thermal defunctionalization of nitrogen-doped carbon nanotubes (N-CNTs) are also under discussion in the present lecture (fig. 1). TGA-MS, low temperature nitrogen adsorption, Raman spectroscopy, HRTEM and XPS were used to trace the changes in the morphology, surface properties and defectiveness of N-CNTs during these processes.