In most European countries upstream activities are assumed more concentrated compared to downstream segments wherein the level of effective competition and deregulation policies plays a crucial role. Globalized oil markets are not homogenous and the characteristics and the degree of competition differ even among the various sub segments of the same oil industry. The oil industry in the EU continues to be dominated by large, integrated and often multinational companies that are active in all stages of oil production (extraction, processing/refinement and retail). They can be distinguished into multinational majors and minimajors - multinational companies that limit their activities to few Member States. Other competitors, predominantly active at the national level. In the USA, the oil industry is dominated by large, multinational companies that are engaged in a wide range of business activities. However, their most important activities are related with the petroleum sector. Most of the oil companies are either fully vertically integrated or independent producers