We determined the oxidative modification of proteins (spontaneous and metal-catalysing oxidation, MKO) and the level of corticosteroids in patients with the depersonalization and depression. For detecting oxidative modification of plasma proteins we measured the concentration of protein carbonyl groups formed with 2,4dinitrophenylhydrazine 2,4dinitrophenylhydrazone derivatives; the formation of dityrosine by fluorescence method; protein aggregation and fragmentation. Polyacrylamide gel electrophoresis with sodium dodecyl sulfate (SDS)-PAGE in the presence beta-mercaptoethanol was used to determine the aggregation or fragmentation of proteins by oxygen radicals (OH). Acid-soluble peptides were analised as products of the fragmentation oxidative modification proteins. The level of the corticosteroids was determined using HPLS. The increase of the concentration of protein carbonyl groups in blood plasma of patients with mental disorders. In patients with depersonalization we determined the increase of the bityrosyl cross-link, and different degrees of fragmentation compared with depressive patients. The cortisol level was decreased and corticosterone was increased in the blood plasma of patients with depersonalization. In depressive patients the cortisol level was increased and corticosterone was decreased is discussed. We discussed the role oxidative modification proteins in the disturbance of the corticosteroid and opioid receptors functions in the patients with mental disorders.