Objective. Benzodiazepine receptors (BDR) in synaptosomal and mitochondrial membranes from different brain areas of alcohol abused patients (postmortem) and the brain cortex of male rats (Vistar line) with different preference to alcohol were studied. Methods. Synaptosomal and mitochondrial receptors of membranes from different brain areas of patients with alcohol addiction and controls were explored using radioreceptor analysis with selective ligands [3H]flunitrazepam and [3H]PK-11195. BDR in the rat brain were studied using [3H]flunitrazepam and [3H]Ro5-4864. Results. An analysis of kinetic parameters (Kd and Bmax) of [3H]flunitrazepam and [3H]PK-11195 binding with synaptosomal and mitochondrial membranes in the human brain showed that BDR was decreased and capacity increased in different human brain areas under the influence of alcohol abuse. The most distinct changes were found in the prefrontal cortex, nucleus caudatus and cerebella cortex. Alcohol abuse induced greater changes in mitochondrial membranes compared to synaptosomal membranes that was consistent with physiological and defensive functions of mitochondrial membranes and CNS under the influence of toxic substances. The affinity of [3H]flunitrazepam and [3H]Ro5-4864 binding with membranes was decreased, but the capacity of receptors was increased in the brain cortex of alcohol-preferring male rats compared to alcohol non-preferring rats. Administration of anticonvulsant meta-chloro-benzhydryl-urea to rats prefer ethanol increased the affinity of BDR.