EN
The effect of visible light exposing on the ortho-positronium formation in polyethylene was studied. Lifetime spectra of positrons in polyethylene were measured in the temperature range between 50 K and 370 K. It was observed that the visible light quenches the enhancement of ortho-positronium intensity (I_{3}) at lower temperature than ca. 250 K - the glass transition temperature of polyethylene. On the other hand, the lifetime of ortho-positronium component (τ_{3}) was not affected by the presence of the visible light.