This thesis concerns US decision-making and policy-making in foreign and defense affairs, at the presidential level. It raises the question of the extent to which formal governmental advisory organizations improve the quality of decision- and policy-making. For this purpose, it analyses and assesses the performance of the National Security Council as an interdepartmental mechanism shaping policies and counselling the President. It also examines the conditions and factors that hinder the activities of the Council, and explains some of its malfunctions. The "bureaucratic" and "presidential" interpretations of policy-making help support this analysis and the enquiry into the performance of the NSC during Nixon and Ford years (1969-1976). The hypotheses are verified through surveys of the literature and several case-studies. The conclusion highlights many complexities of real decision-making in the White House, that supplements some of the explanations offered by both the "bureaucratic" and the "presidential" perspectives.