Article published on the 2008-05-07 Latest update 2008-05-07 13:14 TU
The constitution prevented Putin from standing for a third consecutive term as president but, at the swearing-in ceremony in the Kremlin's gold-leafed Great Palace, he declared that "the responsibility of protecting Russia was and remains my civic duty".
Shortly afterwards, Viktor Zubkov's government resigned and Medvedev appointed Putin prime minister. Nothing prevents him standing for the presidency at the next election.
"It's extremely important for everyone together to continue the course that has already been taken and has justified itself,' Putin said during the ceremony.
His eight years in office have seen economic boom but there is widespread corruption and the government has recently approved big rises in utility prices.
Medvedev, a 42-year-old trained lawyer who has never before held elected office, was backed by Putin during the election which he won by a landslide.
Sam Greene, an analyst at the Carnegie Foundation in Moscow, notes that Medveded didn't mention Russia's difficult relations with the EU and the US in his speech after taking over the post.
The new president promised "a decade of free and stable development" but added that the country "must achieve a sincere respect for the law and overcome legal nihilism".