This study is motivated by a simple yet vitally important question for an understanding of U.S. foreign policy. Quite simply, how does a president's choice of management style influence the U.S. foreign policy decision-making process and decision outcomes? Presidents play a critical role in the formulation of U.S. foreign policy; however, the presidential studies literature and foreign policy analysis literature arrive at very different conclusions regarding how presidents influence the policy process and both are often inaccurate. This study develops an Advisory Systems Typology to address how presidents influence the decision-making process. In addressing this question, this study overcomes the deficiencies of both the presidential studies and foreign policy analysis literature. Four different types of decision-making processes are produced by a president's choice of advisory structure and level of centralization. In addition, the study identifies “unstructured solutions” that indicate how the presidential advisers and president choose to resolve policy disagreements, thereby providing an indication of the decision outcome. The identified decision-making processes and their associated decision outcomes are explored using four cases of decision making on security policy drawn from the Nixon (Vietnam War), Carter (Strategic Arms Limitation Talks II), Reagan (Strategic Arms Reduction Talks I), and Clinton (Bosnia conflict) administrations. The case studies are constructed using the method of structured–focused comparisons, whereby a set of theoretically based questions and anticipated observations to those questions are made in order to guide the research and allow for comparison of decision making within and between cases.