The paper is devoted to instrumental conceptualization of corruption, including classification of its forms and definition of institutional mechanism. It proposes an analysis of conceptual approaches to corruption and demonstrates major aspects of normative approach: value judgment of corruption as an unambiguously negative phenomenon; associating corruption with contempt of law or violation of moral and ethical standards; consideration of corruption as deviant behavior. Author emphasizes challenging issues and ambiguities of this approach. A rationalist approach to corruption, including economic approach, does not address value judgments or norms and standards, but describes in terms of functional assessment its symptoms and consequences. The paper counters the claim that corruption fulfils positive functions such as deregulation and overcoming bureaucratic barriers. The paper reveals a generalized mechanism of corruption: exceeding authority and violating official powers and duties regulations, including code of conduct and ethical standards, and (or) social behavioral, moral, and ethical norms, an official or an administrative organization illegitimately distributes and uses resources of the organization to gain personal or group benefits, not to implement the functions and objectives of the organization. The author proposes a new definition of “political corruption” and describes hierarchy system of types of political and economic corruption, where the “state capture” is at the top. The author also determins institutional mechanism of corruption in the sphere of public power, the essence of which lies in the various types of abuse of its resources. While conceptualizing corruption in public policy in an instrumental way, it is defined as an abuse, misuse of public power resources by a public official not for implementing functions of the state or providing social progress, but for obtaining undue preferences or deriving tangible or intangible personal or group benefits, including gaining advantages in favor of third parties.