Photoemission spectroscopy (PES) is the method of investigation of material that studies the bonding environment and electronic properties of material. The single-walled carbon nanotubes (SWCNTs) have unique properties, and are interesting for different applications. The PES techniques, such as X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) are very useful for studying of filled SWCNTs. Among other functionalization methods, filling of SWCNTs allows modifications of properties of carbon nanotubes in a precise manner. The C 1s XPS spectrum of pristine SWCNTs include a single peak positioned at 284.6 eV. In the UPS spectrum of valence band of the pristine SWCNTs, there are two peaks at 3 eV, and 8 eV. The control of properties during the synthesis procedure and precise investigation methods allow tailoring the properties for applications in nanoelectronics, thermoelectric power generation, light emission. The typical C 1s XPS spectrum of SWCNTs filled with p-dopant, i.e. the spectrum of metal halogenide-filled SWCNTs, includes C 1s XPS peak shifed by 0.3-0.4 eV toward lower binding energies. The C 1s XPS spectrum of SWCNTs filled with n-dopants, i.e. spectra of metal, or molecule-filled SWCNTs, include C 1s XPS peak shifted by 0.05-0.3 eV toward higher binding energies. The changes in XPS, UPS spectra such as shift of peaks, increasing width of spectra, asymmetry testifies about changed electronic properties.