The formation of the gaseous products of polyethylene etching by the action of O(3P) atoms with the participation of O2(b1Σg+), O2(a1Δg), and O2(X3Σg–) oxygen molecules was studied by mass spectrometry. Active oxygen species were formed under irradiation at 147 nm. The main gaseous products were CO2, CO, H2O, and H2. In the pressure range ∼0.2–0.3 kPa, the total quantum yield (ΣΦ) of these products was constant and equal to 4.05. As the pressure was decreased from ∼0.2 to 0.04 kPa, ΣΦ linearly decreased. A mechanism was proposed for the etching of polyethylene at various oxygen pressures.