The powers, functions and duties of prior presidential offices, and their relation with the prime minister and cabinets have over time differed with the various Portuguese constitutions.

Currently, in the Third Republic, a semi-presidential system, the president holds no direct executive power, unlike his counterparts in the United States and France.

Although the prime minister and parliament oversee and direct much of Portugal's actual governmental affairs, the president wields significant influence and authority, especially in the fields of national security and foreign policy, however, always on the advice of the Government and the approval of Parliament.

The president is the supreme commander of the Armed Forces, holds the nation's most senior office, and outranks all other politicians.

The president has the discretionary power to dissolve parliament when he/she sees fit (colloquially known as the "atomic bomb" in Portugal),[7] and President Jorge Sampaio made use of this prerogative in late 2004 to remove the controversial government of Pedro Santana Lopes, despite the absolute majority of deputies supporting the government.

[8] In 2003, President Sampaio also intervened to limit the Portuguese participation in the Iraq War – as Supreme Commander of the Armed Forces he forbade the deployment of the Portuguese Army in a war that he personally disagreed with, clashing with the then–prime minister José Manuel Barroso.