Investors were also wary ahead of Thursday's expiry of options, which could trigger heavy programme-related selling, analysts said.
Wireless operator SK Telecom Co fell 2.65 percent to 183,500 won as its announcement on Tuesday that it would invest up to $280 million in its Vietnam venture sparked worries that overseas investments would reduce dividends.
The benchmark Korea Composite Stock Price Index (KOSPI) closed up 0.07 percent at 1,227.59, its highest finish since October 11 when it hit a record close of 1,244.27.
Shares fell as much as 0.6 percent but rose nearly 1 percent to 1,238.73, not far off from an all-time high of 1,246.41 set on October 5. POSCO Co Ltd, the world's fifth-biggest steel maker, rose 2.35 percent to 218,000 won.
Hyundai Motor Co rose 1.24 percent to 81,400 won, also clawing back recent losses.
Expectations for improving earnings saw Kookmin Bank hit its highest intraday level in 2-1/2 years before ending up 1.7 percent at 65,900 won.
LG.Philips LCD Co Ltd rebounded from early losses to end 1.31 percent higher at 42,600 won.
Samsung Electronics Co Ltd, the world's top memory chip maker, fell 0.33 percent to 601,000 won. The junior Kosdaq market rose for an 8th consecutive session, ending up 0.80 percent at 628.72, its highest close since ending at 631.4 on July 19, 2002.
Trade volume reached 382.1 million shares worth 3.5 trillion won compared to 411.8 million shares worth 3.3 trillion won on Tuesday. Gainers edged out decliners 378 to 368, with 77 titles ending flat.
Foreign investors sold a net 20.2 billion won in shares on the main bourse, while retail investors sold a net 201.7 billion won. Institutional investors bought a net 177.1 billion won. The December KOSPI 200 futures index edged down 0.20 point to 158.20, while the underlying KOSPI 200 spot index gained 0.15 point to 157.87.