The article investigates the effect of rapid thermal annealing of ternary GaAs1-xNx/GaAs solid solutions on the distribution of nitrogen atoms in the crystal lattice. The samples are studied by photoluminescence spectroscopy and high-resolution X-ray diffractometry. Due to the size and electronegativity mismatch of nitrogen and arsenic atoms, nitrogen is incorporated unevenly into the GaAs crystal lattice. Options of the nitrogen atoms arrangement in the GaAs crystal lattice before and after rapid thermal annealing are shown.