* Net profit down 18 percent to $122 million
* Net profit at double the 174 million zloty forecast
* Profit driven by one-offs, tighter spread
(Adds analyst, details, background)
WARSAW, Nov 10 (Reuters) - Polish gas monopoly PGNiG's third-quarter net profit dropped significantly less than expected as lower profits on imported gas were offset by lower provisions, the company said on Wednesday.
Third-quarter net profit dropped 18 percent to 344 million zlotys ($122 million) -- twice as much as analysts expected.
"The results are higher than expectations for two main reasons: significantly lower provisions for exploration risk and a very low tax rate," BZ WBK analyst Pawel Burzynski said.
Burzynski expects the shares, which so far this year gained a modest 2.1 percent, to rise.
The spread between state-set tariffs and import costs is critical for PGNiG, which imports from Russia two-thirds of the 14 billion cubic metres of gas it sells every year.
Import costs are driven by the zloty rate and oil price, while tariffs are set by the regulator, which has often declined to raise them by as much as and as often as PGNiG wanted.
The latest hike took place in October, but a recent rally in the zloty raised questions about a potential cut in the tariff.
PGNiG estimates prices of imported gas rose 47 percent year-on-year and it earned only 83 million zlotys in the segment, down from 508 million year earlier. (Reporting by Patryk Wasilewski; Editing by Louise Heavens)