UPDATE 1-S.Korea economy contracts in Q4 on strong base effect, holidays

(Adds details, Bank of Korea comment)

* Q4 GDP -0.2 pct s/adj q/q (Reuters poll +0.1 pct)

* Q4 GDP +3.0 pct y/y (Reuters poll +3.1 pct)

* Exports -5.4 pct q/q, facility investment -0.6 pct q/q

* Private consumption +1.0 pct q/q

SEOUL, Jan 25 (Reuters) - South Korea's economy contracted in the December quarter, missing forecasts and marking its worst quarterly performance since 2008 on a strong base effect and as a long autumn holiday held back industrial production.

Gross domestic product fell by a seasonally adjusted 0.2 percent in the fourth quarter, the Bank of Korea said on Thursday, slowing from a bumper growth of 1.5 percent in the third quarter, the fastest expansion in seven years.

Full-year GDP growth for 2017 was 3.1 percent versus 2.8 percent in 2016.

The contraction in fourth-quarter 2017 undershot the 0.1 percent expansion seen by economists and marks the worst quarterly performance since the economy contracted by 3.3 percent on-quarter in the fourth quarter of 2008.

The economy expanded 3.0 percent from a year earlier, slowing from 3.8 percent growth in the September quarter.

"(The contraction) is from the base effect as the third quarter posted a very high 1.5 percent. The Chuseok holiday shortened the number of working days in October, which had hurt factory activities. But growth momentum is solid here and ongoing," a BOK official said after the data was released.

Thursday's data reinforced a broad consensus that the central bank's monetary tightening will be gradual this year as export- and investment-led growth moderates after rapid expansion in 2017.

The BOK is monitoring the effects of its November hike, the first tightening in six years, and remains wary of triggering disruptive capital flows.

The BOK held its policy interest rate unchanged at 1.50 percent on Jan. 18 and upgraded its 2018 growth forecast to 3 percent, a fraction higher than the 2.9 percent projected in October last year.

It lowered its 2018 consumer inflation forecast to 1.7 percent from 1.8 percent, supporting analysts' views that monetary policy will remain accommodative in 2018.

Exports contracted by 5.4 percent in the fourth quarter after jumping 6.1 percent a quarter earlier, while private consumption growth accelerated to 1.0 percent from 0.8 percent, the BOK said in a statement.

The drop in exports was also seen as a base effect while a fall in car exports offset soaring overseas sales of memory chips, the central bank said.

Construction investment fell 3.8 percent from a quarter earlier after the government said in October it would impose additional mortgage curbs on owners of multiple homes to discourage excessive borrowing.

(Reporting by Cynthia Kim; Editing by Eric Meijer)