Profits at Russian gas export monopoly Gazprom for the six months to June are 10 times the level of the year before.
The company said it made 103.76bn roubles ($3.48bn, £2.08bn) thanks to strong exports, on sales that rose 38%.
But the performance - which was far ahead of expectations - failed to lift the firm's shares in Moscow.
Investors blamed a $227m loan guarantee given to a company which will resell Gazprom's gas in Poland for the continuing concerns.
The deal means the company - Eural TG, registered in Hungary - is effectively competing with Gazprom's own monopoly in selling gas delivered to Poland via its pipeline from Turkmenistan to Ukraine.
Eural TG already resells the gas in Ukraine.
A Gazprom spokesman said the deal was dictated by Ukraine, in its position as the key transit country.
"We didn't really have a choice," the spokesman, Sergei Kupriyanov, told Reuters.
"But the deal will at least give us a chance to closely monitor all gas re-export transactions."
Gazprom shares were up 2% on Moscow's RTS index at lunchtime.