We have conducted a feasibility study on the development of offshore wind farms around the Korean Peninsula as part of the national plan. This study deals with the selection of the optimal site for an offshore wind farm. We set rating indices in order to select an optimal site of the candidate coasts, which include the expected B/C (benefit to cost) ratio, the possible installation capacity of the wind farm, the convenience of grid connection, and so on, for each candidate site. The expected B/C ratio is described as the benefit from the annual energy production compared to the costs that correspond to the construction of the turbine foundation, and the grid connection between the offshore wind farm and the substation on land. It can be found from the evaluation that the construction costs associated with the substructure and grid connection are crucial in determining the location of the first offshore wind farm in Korea. Consequently, we could select a top site among the candidate sites to be implemented as the first national project of offshore wind farm development. (C) 2012 Elsevier Ltd. All rights reserved.