With reference to our recent reports [ Appl. Phys. Lett. 90, 192107 (2007) ; Appl. Phys. Lett. 91, 202102 (2007) ] about the electronic structure of chlorine treated and oxygen-plasma treated nitrogenated carbon nanotubes (N-CNTs), here we studied the electron field emission effects on chlorination (N-CNT:Cl) and oxidation (N-CNT:O) of N-CNT. A high current density (J) of 15.0 mA/cm2 has been achieved on chlorination, whereas low J of 0.0052 mA/cm2 is observed on oxidation compared to J = 1.3 mA/cm2 for untreated N-CNT at an applied electric field EA of ∼ 1.9 V/μm. The turn-on electric field (ETO) was ∼ 0.875. The 1.25 V/μm was achieved for N-CNT:Cl and N-CNT:O, respectively, with respect to ETO = 1.0 V/μm for untreated one. These findings are due to the formation of different bonds with carbon and nitrogen in the N-CNT during the process of chlorine (oxygen)-plasma treatment by the charge transfer, or else that changes the density of free charge carriers and hence enhances (reduces) the field emission properties of N-CNTs:Cl (N-CNTs:O).