Dmitry Medvedev was sworn in as Russia's third president at a Kremlin ceremony on Wednesday that stressed the continued authority of his predecessor Vladimir Putin.
Medvedev "has assumed the office of President of the Russian Federation," Valery Zorkin, head of the constitutional court, said after Medvedev pronounced the oath of office with his hand on a copy of the constitution.
The Kremlin Palace ceremonywas held in front of 2,400 invited guests.
It began with an honour guard bringing in the symbols of the presidential office.
Although brief, the inauguration is not being under-stated: with the Russian flag, presidential standard and a copy of the country's constitution being borne aloft into to the hall where Mr Putin is making a speech before handing Mr Medvedev the chain of office.
The grand ceremony is the expression of a new confidence that oil- and gas-rich Russia now feels, correspondents say.
Mr Medvedev, 42, won a landslide victory in the March elections. The inauguration will cap his sharp ascendance from obscurity.
But while Vladimir Putin is handing over the reigns of power, his central role in the ceremony will reflect the part he has to play in Russia's future.
However, analysts suggest he will remain a pivotal figure in Mr Medvedev's administration after he assumes his new post of prime minister, possibly as early as Thursday.
Having campaigned as Mr Putin's protege and tied himself to his mentor's policies as soon as his victory became known, analysts say it is no surprise that Mr Putin will continue to play a central role.
An economic liberal, Mr Medvedev has served Mr Putin as first deputy prime minister, chairman of Gazprom - Russia's enormous state-run gas monopoly, campaign chief and chief of staff.
A lawyer by training, in the 1990s Mr Medvedev was an assistant professor at St Petersburg State University, during which time he became an expert consultant for the city's mayor - one Vladimir Putin.
And, analysts suggest, their partnership looks set to continue.
On the same day, Russia's government led by Prime Minister Viktor Zubkov resigned, opening the way for Vladimir Putin to be appointed to the post after his successor Dmitry Medvedev was sworn in as president.
"Zubkov signed a government order... concerning the resignation of the government on May 7, 2008 before the newly elected president of the Russian Federation," the government said in a statement.