Removal processes of nitric oxide (NO) in pulsed corona discharges were observed by laser-induced fluorescence (LIF) imaging spectroscopy in a reactor filled with N-2/NO mixtures. Distributions of NO along the streamers and effective energy costs of NO removal (epsilon(rem)) obtained from the LIF images were compared with these predicted by a model taking account of the diffusion. For an initial NO concentration [NO](0) of 1000 ppm epsilon(rem) was 120 +/- 31 eV/molecule, while it was increased up to 620 +/- 160 eV/molecule for [NO](0) of 30 ppm, due to a higher recombination loss of the reducing species of the nitrogen atoms.