CD Projekt has said The Witcher 2 moved 1,110,055 units on PC in 2011. The digital version sold 270,000 through digital distribution services, and 40,000 of those were through GoG.
The sequel's sales also bolstered sales of the original title, which moved 401,543 copies last year.
The game was released in May of 2011 and by August had already moved 940,000 units with 400,000 sold in its first week.
"I have to admit, though, that the sales results for The Witcher, five years on from the game's premier, are remarkable," CDPR managing director Adam Badowski told Eurogamer. "If anything, they prove that the content we put into our games ages well.
"The Witcher will continue to generate buzz in the coming years."
The Witcher 2 will land on Xbox 360 April 17, and the firm has numerous titles in the works.