Chronic social defeat stress in daily agonistic interactions leads to the development of mixed anxiety/depression state in male mice. This paper aimed to study the effects of chronic diazepam treatment on the psychoemotional state of these animals. Diazepam (0.5 mg/kg, i/p, Polfa Tarchomin S. A.) or saline was chronically injected into male mice for two weeks on the background of continuing agonistic interactions (preventive treatment) or into male mice with mixed anxiety/depression state after stopping of social confrontations (therapeutic treatment). Then, the animals were studied in the partition, plus-maze and Porsolt' tests, estimating the levels of communicativeness, anxiety and depressiveness, respectively. Preventive diazepam treatment had a weak protective anxiolytic and pro-depressive effect. The therapeutic diazepam treatment didn't influence on the anxiety and depression-like state. Chronic diazepam was ineffective for the treatment of the mixed anxiety/depression state in male mice. Different effects ofdiazepam on anxiety and depression-like states under preventive treatment confirmed our conclusion shown earlier about the independent development of these pathologies at least in our experimental paradigm.