The differences of cholesterol and fatty acid content of silicone oils that were removed from vitrectomized eyes due to different retinal diseases were investigated. The silicone oils were removed from 25 cases after 4-8 months and classified in two groups; Group A consists of 11 patients who had undergone pars plana vitrectomy combined with phacoemulsification and intraocular lens implantation due to diabetic tractional retinal detachment and Group B consists of 14 patients who was treated for phakic primary rhegmatogenous retinal detachment. The removed material from vitrectomized eyes in Group A was opacified and gelatinous on the other hand in Group B it was transparent. Hexan extracts were prepared from liquid and emulsified phases. The extracts were taken into vials, after that, hexane was removed. The chemical structure of each extracted material was investigated by spectroscopic techniques. The concentration of unsaturated fatty acids (FAs) in both groups were compared statistically. In conclusion, in Group A, epoxy and hydroxy-epoxy FAs were determined. The mean amount of unsaturated FAs in Group A was significantly lower than Group B. Cholesterol was not detected in any samples. The type of FAs in removed silicone oils may differ depending on the oxidative stress of retina.