The poster, which read "Save the Arctic" and "Show Gazprom the red card" and featured the logo of the environmental protest group, appeared shortly after the news conference in the Danish capital began and was quickly removed by an official.
Gazprom are one of the sponsors of Europe's elite club competition and the poster blocked out the state-owned Russian oil giant's logo on the set behind Ancelotti, who appeared bemused by the incident along with Real defender Pepe.
Copenhagen could face a stiff UEFA sanction over the protest.
Swiss club Basel were fined 30,000 euros ($41,200) by European soccer's governing body after Greenpeace activists interrupted their Champions League match against Schalke 04 in October with a protest against Gazprom.
Play was halted for around five minutes when four people wearing orange boiler suits and helmets descended on ropes dropped from the stadium roof and waved banners reading "Gazprom, don't foul the Arctic".
UEFA said Basel had been fined for "insufficient organisation".
Russian courts last month granted bail to nine jailed Greenpeace activists, part of a group of 30 facing trial over a protest against Arctic oil drilling.
They are charged with hooliganism after some tried to scale an oil platform in the Pechora Sea, Russia's first offshore rig in the Arctic.
Greenpeace believes drilling for oil there threatens the region's pristine environment, while the Russian government says development and shipping there are important to the nation's economy and security.
(Writing by Iain Rogers in Madrid, editing by Ed Osmond)
