Objective. To evaluate gender effects on the correlation between cortisol, molecular products of lipid peroxidation (LPO) and carbonylation of proteins in patients with heroin addiction. Material and methods. Authors examined 82 patients, 49 men and 33 women, with heroin addiction. Biochemical and statistical methods were used. Results and conclusion. Gender differences in the carbonylation of proteins were noted. In men, but not in women, the low level of cortisol was associated with an increased content of carbonylated proteins. In women the level of these proteins was lower than in men. Gender did not exert an effect on LPO.