Among the seven are the two men tapped both by opinion polls and political commentators to be the main contenders.
They are current Prime Minister Viktor Yanukovych, who has the backing of incumbent President Leonid Kuchma, and the leader of the center-right opposition coalition Our Ukraine bloc, Viktor Yushchenko.
The other candidates who have registered so far are Socialist Party Chairman Oleksandr Moroz; Communist Party leader Petro Symonenko; the leader of the Progressive Socialist Party, Natalya Vitrenko; the leader of the United Family Party, Alexander Rzhavsky; and Slavic Party leader Alexander Bazilyuk.
Others likely to register include Igor Dushin, head of the Liberal Democratic Party, and Anatoly Kinakh, president of the Party of Industrialists and Entrepreneurs.
Kuchma, in his second term, has said repeatedly he will not run again. The country's constitution limits the president to two terms. But Kuchma secured a controversial ruling from Ukraine's Supreme Court that would allow him -- on a technicality -- to run again.
Some political observers believe he may yet decide to do so.
Ivan Lozowy is the director of the independent Institute for Statehood and Democracy think tank in the Ukrainian capital, Kyiv. Lozowy says the pro-government forces are not completely unified.
"That means, in my opinion, that the possibility of some serious upheavals, including the announcement of Leonid Kuchma running for the presidency, remains," Lozowy says.
But Lozowy believes the chances are slim, and that Yanukovych is seen as the candidate to prolong the present government's policies and keep most of its key people in power.
The opposition, as well as Western governments and institutions, accuse Kuchma's administration of corruption, election rigging, and abuse of human rights -- leading to greater international isolation for Kyiv.
Lozowy says this isolation will continue if the country's next president emerges from the Kuchma camp, which would likely push Ukraine even closer to Russia.
Yanukovych last weekend told a congress of the political party he leads -- the Party of the Regions -- that he wants to tackle corruption and poverty. He also promised to complete reforms aimed at privatizing land and at turning Ukraine's huge, unwieldy conscript army into a compact, professional force.
Yanukovych says he will end poverty by boosting tax collection among the country's wealthy businessmen. He said: "I will not only stop tax holidays, but I will make them pay back taxes. Then we can all forget about poverty."
Opposition leader Yushchenko on 4 July addressed a rally of around 70,000 supporters in a Kyiv park and promised to fight high-level corruption, increase wages and pensions and to create "millions" of new jobs.
Yushchenko, a former prime minister, portrays himself as the people's candidate fighting against the corrupt authorities. Yushchenko is seen as pro-Western.
Yanukovych also says he wants to develop closer relations with the West, but not, he says, at Russia's expense.
Although both men profess many of the same goals, Lozowy says they are two very different politicians -- for example, when they talk about fighting corruption.
“Firstly, Yanukovych is the product of a system that is almost entirely corrupt. Secondly, Yushchenko is a self-made man.” Yanukovych says Yushchenko is independent, and that people explain his high popularity by the fact that people believe what he says.
Most opinion polls put Yushchenko in first place with 25 to 27 percent of the vote, and Yanukovych second with 17 or 18 percent.
Yanukovych's most powerful backer is the Social Democratic Party-united, led by the head of President Leonid Kuchma's presidential administration, Viktor Medvechuk.
Lozowy says that although Yanukovych enters the race behind Yushchenko, he has the advantage of having many powerful government tools at his disposal.
"Viktor Yanukovych is going to receive and benefit from serious and powerful resources of the administration to increase his ratings [in the polls]. In the first place, there is the Ukrainian state budget -- that is, money -- and all the mass media which is controlled by people linked to the government or directly by the government," Lozowy said.
All sides warn the election is likely to be dirty.
Lozowy says he agrees with this assessment. “There's already been a book produced to discredit Yushchenko, and a film is being prepared. All of this is done by insignificant people, but it is inspired and financed by people close to the head of the presidential administration, Viktor Medvechuk, and other people from Kuchma's circle."
If no candidate gets more than 50 percent of the vote, there will be a runoff two weeks later between the two top candidates.
Lozowy does not think anyone will win outright in the first round.
"In today's circumstances, with the current distribution of [political] forces, it's almost impossible. In my opinion, it would only be possible if there was a complete falsification of the election results," Lozowy says.
He thinks both Yanukovych and Yushchenko will reach the runoff.
Registration of candidates ends on 7 August.