Article 1 of the “Act on Private Participation in Infrastructure of Korea” states that the Act aims at contributing to the development of national economy, by promoting private investments in public infrastructure in order to establish and operate more creative and effective infrastructure. In order to meet this goal, it is an essential prerequisite to legally establish a project structure which ensures some appropriate returns to the private sector participating private investment projects.The main focus of this research paper is to review some relevant provisions of the Act to find out whether such provisions can provide some adequate returns as well as profits to private concessionaires in the private sector, and, if not, what kinds of alternatives can be recommended to promote private investment. Some of controversial issues discussed in this paper are: whether the relationship between the transfer of ownership to the Authority and the free use of infrastructure by the private investor is based on a bilateral contract between the two; and whether the period of free use for the private investor should be measured by the total project profits and costs.In case of revertible projects such as BTO(Build-Transfer-Operate), BTL(Build-Transfer- Lease), and BOT(Build-Operate-Transfer), the ownership of infrastructure completed under the private-public participation projects will be transferred to the authority such as a state or local government while the private investor will be entitled to use such infrastructure free of charge for a specified period. This legal arrangement is a kind of contract between the public and the private sector, not a separate legal action.In addition, a private investor must be willing to invest if a private investment recovery structure assures its profits and returns on its investment. However, the Korean Act permits a private sector to use the infrastructure for a ceratin period of time based on only the total project costs, not on the sum of the total project costs plus project profits. Thus, the Act fails to provide a legal framework for a private investor to recover adequate returns from its investment for such a limited period. Thus, it is worth considering other laws such as the Act on Toll Road in Korea or the German Private Financing Law on Through Roads Construction (Fernstrassenbauprivatfinanzierungsgesetz) which considers the rate of return when the user fees, as the recovery of the investment, are decided.Since project profits or the rates of return are closely related to the competent authority and the infrastructure user who pays for user fees, it is important to specify some provisions which guarantee some adequate returns to the project investors.