This article briefly considers possible reasons why some states prefer production sharing agreements (PSAs), some prefer licences and others prefer a combination of the two when developing their oil and gas resources. Outlines key distinctions between the mechanisms and how the choice of approach may be influenced by factors including: (1) whether a state is developed or developing; (2) the duration of the exploration; (3) whether flexibility is required; (4) the investment risk; (5) the degree of regulatory measures involved; and (6) levels of competition