"Yes... it is difficult. In the Curia, there are also holy people, really, there are holy people. But there also is a stream of corruption, there is that as well, it is true... The 'gay lobby' is mentioned, and it is true, it is there... We need to see what we can do," the pontiff said.
He did not specify what kind of action he might take.
Francis made the remark during an audience with members of the Latin American and Caribbean Confederation of Religious Men and Women (CLAR).
He also signalled his support for the reform of the government of the Catholic Church.
"The reform of the Roman Curia is something that almost all Cardinals asked for in the Congregations preceding the Conclave. I also asked for it," Francis said.
In February last year, the Vatican attacked Italian media reports of a powerful "gay lobby" inside the curia, citing a confidential report commissioned by the previous pope, Benedict XVI.
Benedict ordered the report after leaks of private papal documents to Italian media that laid bare corruption and venemous infighting in the Vatican.
His former butler, Paolo Gabriele, was jailed for the leaks but was released after Benedict pardoned him.
The "Vatileaks" report was prepared by a three-cardinal commission. It uncovered a lobby of "worldly" gay prelates that could affect individual promotion prospects and wielded "external influence", the La Repubblica daily said.
Shortly before Benedict abdicated in February, the Vatican said the report would "remain solely at the disposition of the new pope".
There has been speculation that the alleged gay lobby's power had influenced Benedict's decison to step down.