X-band field-sweep electron spin echo and pulsed electron nuclear double resonance (ENDOR) spectroscopy were used to study n-type 15R SiC wafers grown under carbon (C)-rich conditions with the aim to verify the recently proposed concept that nitrogen (N) donors substitute both carbon (C) and silicon (Si) sites and may occupy nonequivalent positions at Si sites. It was found that besides the 14N ENDOR spectra of the C substituting quasicubic "k1", "k2", and "k3" positions five doublet lines due to 14N nuclei at other lattice positions were observed in the ENDOR spectrum of highly compensated C-rich n-type 15R SiC. Three of them with the hyperfine interaction (HFI) constants 34.66, 32.20, and 29.77MHz were attributed to the N donors substituting "k1", "k2", and "k3" positions at Si sites. Two other additional ENDOR spectra were explained by the presence of the C antisite (CSi) defects in C-rich 15R SiC, which leads to the formation of CSiNC complexes with donor levels close to the conduction-band minimum and is