ZnSe:N samples with different doping levels have been exposed ex situ to hydrogen (H) or deuterium (D) plasma. Secondary ion mass spectroscopy reveals that the H/D profile matches exactly the N profile in all samples, whatever the plasma-exposure conditions. All samples are semi-insulating after H/D exposure. Photoluminescence spectroscopies show that the deep-compensating donor is N-related, which help in discarding a few plausible mechanisms. Finally, our results also confirm that the main shallow-compensating donor in ZnSe:N is a N-related defect.