The discussions in the border truce village of Panmunjom had no fixed agenda, but aimed to cover a range of "major" issues, including a planned February 20-25 reunion for family members divided by the Korean War.
A short morning dialogue was followed by three hours of discussions in the afternoon, after which the two chief delegates began a one-on-one session at 7:15pm (1000 GMT).
The South delegation was led by top National Security Council official Kim You-Hun, who said Seoul's focus was on ensuring that the reunion went ahead as scheduled.
Before the talks began, Kim promised to keep "an open attitude to explore the chance of opening a new chapter on the Korean peninsula".
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He did not mention whether North Korea's nuclear programme would be discussed.
It was the first such high-level sit-down between the two sides since 2007, and came a day before US Secretary of State John Kerry's arrival in Seoul for a brief visit focused on North Korea.
The Panmunjom meet was requested by Pyongyang and made front-page headlines in the South.
But it barely merited a mention in the North's state media, with the official KINA news agency putting out a one-line despatch on Wednesday.
Kim Yong-Hun, a North Korean expert at Donging University in Seoul, said Pyongyang was keen to make a public display of its diplomatic credentials.
"It wants to demonstrate a willingness to improve ties with the South in order to obtain concessions from Seoul and others," said Kim, who warned it was premature to expect any major breakthrough.
The South suspended the tours after a tourist was shot and killed by North Korean soldiers in 2008, and Pyongyang is keen to see the return of what was a lucrative source of hard currency.