The key election is being seen as a referendum on Mr Olmert's bold vision to finalise the final borders of Israel and unilaterally separate from the Palestinians.
Pre-election polling put Mr Olmert, who was catapulted to power when Prime Minister Ariel Sharon suffered a massive stroke 12 weeks ago, in front, despite leading a centrist party that was only formed late last year.
However it is expected to need support from other parties to ensure parliamentary approval to implement the pullout plan.
"Bold vision"
"We are not going to be able to fulfil all our dreams," Mr Olmert wrote in an opinion piece for the top-selling Yediot Aharonot newspaper.
"We must preserve the main settlement blocs in Judea and Samaria (the West Bank) and we will fix the route of the security barrier beyond which we will no longer remain."
The barrier being erected across the occupied West Bank fences off the majority of the quarter of a million Jewish settlers from the 2.5 million-strong Palestinian population.
Casting his ballot, Mr Olmert urged others to do the same, amid fears that voter turnout could be low.
"Go and vote and may this be a beautiful day for the people of Israel," he said.
Tight security
About 22,000 police are being stationed outside the 8,000-plus polling stations, and troop reinforcements have been deployed across the country to try to prevent militant attacks.
Police restricted access to the flashpoint Al-Aqsa Mosque/Temple Mount compound, holy to both Jews and Muslims.
According to final pre-ballot opinion polls, Kadima will win 34 seats in the 120-member parliament despite fears of voter apathy which may favour right-wing or religious parties.
The Yediot Aharonot newspaper forecast 21 seats for the centre-left Labor and 13 for the right-wing Likud while a rival poll in the Maariv gave Labour 17, Likud 14 and the extreme right-wing Yisrael Beitenu 12.
Polls predicted that the Labour party, led by Amir Peretz, would emerge the second force in parliament.
Voter apathy
But many Israeli voters showed little interest during election campaigning.
Kadima's proposal to give up some West Bank settlements and strengthen others to impose a border with the Palestinians is popular among Israelis tired of conflict.
Some analysts also saw the victory of Hamas in Palestinian elections earlier this year as a factor, noting that even more dovish parties were not talking of peace with a group that is formally committed to destroying Israel.