Previous research on offshore wind farm (OWF) siting has been dominated by studies centred on energy resources and profitability, human activities and acceptance. Recently, studies on environmental impacts of OWFs have emerged. Few studies have been carried out to discuss the issues comprehensively. This study develops a set of comprehensive OWF siting criteria; including the profitability, social, security and environmental considerations. It solicits expert opinions from academia and industry through an international Delphi method. Contrary to the typical consensus seeking in Delphi studies, it focuses on understanding the dissensus through a comprehensive discussion. We find that profitability and social considerations are the most commonly agreed siting criteria among the experts whereas environmental and security criteria receive less agreement. As OWFs move further offshore, we are concerned about the understanding of the associated environmental impacts, and how energy and marine policy affect the marine spatial planning and consenting process. Research must get ahead of the developments to provide a better understanding of the potential impacts and to guide the consenting and monitoring processes.