Background /Aim. Cataract is a structural, biochemical and optical change in the eye lens, which changes transmission and refraction of light rays reducing keenness and clarity of a figure on the retina. Its occurrence is highest in older people, over the age of 65 (45.9%), thus a certain degree of opacification exists practically in all people over the 70. Our research was directed to measuring of lipid peroxidation products in cataract lenses involved in early stages of cataractogenesis through oxidative stress and in the development of mature cataract. Methods. Clinical and biochemical research was carried out in 101 patients with cataract, 46 women and 55 men. The average age of the group was 72.47 (ґ = 7.98). According to the cataract maturity degree the patients were classified into two groups as follows: cataracta senilis incipiens (n = 41) and cataracta senilis matura (n = 60). Measuring of diene conjugates was carried out by spectrophotometer. Fluorescent lipid peroxidation products were measured by a spectrofluorophotometer, and malondialdehyde (MDA) concentration was measured by colorimeter as a product of a reaction with thiobarbituric acid (TBA). Result. Significantly higher diene conjugated concentration in lenses was measured in the patients with the diagnosis cataracta senilis incipiens (p < 0.001) as well as the intensity of fluorescent iminopropens (p < 0.001). Significantly higher MDA concentration in lens (p < 0.001) was measured in the patients with cataracta senilis matura. Conclusion. The lens structure changes caused by lipid peroxidation can, with other risk factors present, influence the occurrence and development of mature cataract. Some cataract types show different lipid peroxidation intensity with the most distinct changes in cataract which started as corticonuclear.