In modern Russian criminal law means diminished responsibility, that the subject is not capable to regulate meaningly legally significant behaviour at the moment of socially dangerous act. Such disability comes at presence if the subject has the chronic or time mental disorder, an aphrenia or other disease state of mentality. The specified clinical phenomena define medical criterion of diminished responsibility. Special interest represents disorders which in ICD- 10 concern to «Personality Disorders» (F60-F68). Here mental disorders which have no so-called remedial basis are meant, or in their structure it is impossible to note signs of weakening process. At the same time they not only qualitatively differ from the accepted norm, but also under known conditions possess that depth or expression that can be regarded as medical criterion of the formula of diminished responsibility. The research which has been spent in the Department of psychogenias and personality disorders of Institute of Serbsky included 80 men at the age from 20 till 45 years by which the diagnosis «Personality disorder» was established. It has shown that there can be 3 variants of influence on responsibility: they can cause full loss of liability; can essentially reduce the criminal liability; their presence can be neutral and not render influences on liability. The analysis of expert judgements shows, that in expert judgements about disability of the subject to regulate the behaviour meaningly it is necessary to estimate components both medical, and psychological criteria of diminished responsibility.