The substitution of selenium oxyanions in the hydroxyapatite structure was examined using multinuclear solid-state resonance spectroscopy (ssNMR). The study was supported by powder X-ray diffractometry (PXRD) and wavelength dispersion X-ray fluorescence (WD-XRF). Samples of pure hydroxyapatite (HA(300)) and selenate (HA(300)-1.2SeO(4)) or selenite (HA(300)-1.2SeO(3)) substituted hydroxyapatites were synthesized using the standard wet method and heated at 300 degrees C to remove loosely bonded water. PXRD data showed that all samples are single-phase, nanocrystalline hydroxyapatite. The incorporation of selenite and selenate ions affected the lattice constants. In selenium-containing samples the concentration of Se was very similar and amounted to 9.55% and 9.64%, for HA(300)-1.2SeO(4) and HA(300)-1.2SeO(3), respectively. PXRD and ssNMR data showed that the selenite doping significantly decreases the crystallite size and crystallinity degree. P-31 and H-1 NMR experiments demonstrated the developed surface hydrated layer in all samples, especially in HA(300)-1.2SeO(3). H-1 NMR studies showed the dehydroxylation of HA during the selenium oxyanions substitution and the existence of hydrogen bonding in structural hydroxyl group channels. (HSe)-H-1-Se-77 cross polarization NMR experiments indicated that selenites and selenates are located in the crystal lattice and on the crystal surface.