An ultraviolet laser was used to irradiate the screen-printed carbon nanotube (CNT) cathodes in air, N-2, and O-2 atmospheres in various pressures. The emission current density of CNT cathodes at a field of 6.6 V/mu m was increased by a factor of 400 after laser irradiation in an O-2 atmosphere, which was enhanced by the increase in O-2 pressure. On the other hand, N-2 has less influence on the laser irradiation effect. The enhancement in electron emission by laser irradiation in air was found to be 20% of that in an O-2 atmosphere with the same pressure, because of the partial pressure of the oxygen in air. (c) 2005 American Vacuum Society.