High-resolution pure rotational spectra of nitrosyl fluoride, FNO, and nitryl fluoride, FNO2, have been measured using a cavity pulsed microwave Fourier-transform spectrometer. The samples were prepared using a pulsed electric discharge through precursor substances, with the discharge apparatus mounted as part of the pulsed nozzle of the spectrometer. Nuclear quadrupole and magnetic hyperfine structures due to 14N and 19F have been resolved for both molecules, and precise values for the nuclear quadrupole and spin–rotation coupling constants have been obtained. The 14N quadrupole coupling constants of FNO2 have been rationalized in terms of a σ-withdrawal of electron density from NO2 towards F. This view is corroborated by the magnetic shielding estimated from the F spin–rotation constants.