3096 Days documents the harrowing eight and a half years that Kampusch was held captive by Wolfgang Priklopil after he abducted her near the Austrian capital aged 10 in 1998.
The film is based on the book that the 25-year-old wrote following her escape in 2005. Priklopil committed suicide shortly afterwards.
Kampusch, who at one point weighed just 84lbs during her captivity, kept a diary which she wrote on loo paper and stored in a box.
Meanwhile, Campbell-Hughes made headlines and shocked fans after she revealed her extreme weight loss to play the role of Kampusch. The 30-year-old Albert Nobbs star attended a BFI Film Festival premiere last year and exposed her emaciated figure in a sheer blue dress.
Speaking about the role at the premiere yesterday, Campbell-Hughes told reporters: "It was a very isolated time, it was a bubble of time, and I wanted to keep that very focused."
Kampusch declined to give interviews.