The present work aims to highlight the influence of water molecules in the photo-decomposition of methane ice and reveal the photoproducts formed in solid phase upon VUV irradiation of CH 4-H 2 O mixture in methane-rich ices. The analysis of our IR spectra shows that even with very low concentrations of water in methane ices, several oxygenated hydrocarbons are formed as photoproducts derived from the photodecomposition of water and methane at cryogenic temperatures. We show that both alka[e]nes and oxygen bearing organics are efficiently formed at temperatures as low as 3 K. However, while the IR signatures of the alka[e]nes such as C 2 H 6 , C 2 H 4 and C 2 H 2 dominate the IR spectra of the irradiated CH 4-H 2 O ices at temperatures lower than 50 K, the heating of the sample to 110 K reveals the formation of large carbon chain complex organic molecules such as ethanol, pronanol, porpanal and glycolaldehyde.