The article deals with the concept of investment activity, its generic and specific characteristics through such features as prerequisites for activity, purpose and means of activity, conditions of activity; legal forms of implementation and forms of public organization; the system of other the basic concepts of investment law and investment legislation, such as investments, investor, customer, service provider, user, and others. The author describes the major legal forms of investment relations and, in particular, investment agreements involving public law entities: special investment contracts, agreements on public-private partnerships, concession agreements, production sharing agreements. These investment agreements involving public law entities (special investment contract, agreement on public-private partnerships, concession agreement, and production sharing agreement) are defined as multilateral deals. The multilateral nature of the said investment agreements makes them different from bilateral investment agreements involving public law entities, namely procurements for public needs, work contracts for public needs, lease of the public property, trust management of the public property and other bilateral deals. The article also assesses the role and limits of public organization of investment activity. The author comes to the conclusion about the excessive character of legislative regulation of investment relations involving public law entities. It is noted that the practices of project management developed by business by definition cannot be used effectively in the public sector, since businesses and public authorities have fundamentally different incentives for their activity. The business seeks to maximize profits and get other benefits, while the state aimes at the public utility which is often understood in the way in which it is understood by public authority officials. The state should guarantee and protect economic interests of the business, rather than to participate in the economic activity and regulate it (in a legislative and administrative way). Government regulation must be carried out to the extent that is necessary and sufficient to protect the society from the conduct of persons infringing the rights and interests of others.