The article presents a relatively integrated totality of psychological knowledge, covering the main areas of activity and functions of the police officers as well as their professional self-development and maintenance of the necessary personal and functional mental state. The Author studies the system of psychological knowledge relevant to the police activities. This knowledge system is determined by the content of professional police activities, its functions and tasks. Psychological knowledge necessary in the work the police officers is not limited to the knowledge useful for effective implementation of professional functions. Along with these there is relevant psychological knowledge and recommendations on ensuring the normal state of their own nervous and mental resources considering stressogenic activity and high nervous and mental stress as well as the knowledge necessary for professional and personal self-development, including auto-correction of psychological deformations caused by professional activity. This knowledge and recommendations represent an independent branch of scientific and psychological support of police activities. The author believes that in the detection of illegal acts, exposure and bringing perpetrators to account, for example, such sections of psychological knowledge appear relevant as: a psychological characteristic of offences, personal psychological prerequisites of unlawful behaviour and the nature of criminality in the psychological structure of the personality, the main parameters of the psychological assessment of criminal groups , the importance of various mental states and properties of human personality as the internal causes of behavior, psychological recommendations for communication with various categories of citizens to identify the perpetrators and expose crimes, psychological recommendations for effective conducting of search operations in detecting crimes and their investigation.The author describes the main types of psychological skills and professionally important personal qualities, the formation of which provides a high level of professional competence of the police officers.