Polanski said he discovered while filming a new version of the Charles Dickens novel that his own childhood as an orphan during World War II in Poland allowed him to identify with the film's penniless title character.
Polanski's parents were sent to Nazi death camps, and his mother died at Auschwitz. He escaped the horrors of Poland's Krakow ghetto, living off the charity of strangers in the countryside until his father reappeared to claim him.
"I knew how people treat a child whose parents are dead," Polanski, dressed casually in a blue blazer and jeans, told reporters in downtown Warsaw.
Like Oliver, Polanski said he knows what it's like "to walk for kilometers without socks in boots with bloody feet."
"Above all, I knew that the worst thing isn't a hard bed or hunger, but having no parents," he said.
The 72-year-old Polanski, director of the Oscar-winning film "The Pianist," was in Warsaw to promote the film. It debuted last week in the Czech Republic, where it was filmed, and opens in theaters Friday in the United States and Poland.
The film is based on Dickens' classic tale of a young orphan turned pickpocket in the squalor of Victorian London.
But to Polanski, the tale is timeless.
"Of course the story's aged - but the Bible has too," he said.
While in the Polish capital, Polanski said he also plans to spend some time overseeing the Polish adaptation of the musical "Dance of the Vampires," based on the director's 1967 film of the same title. The musical opens in Warsaw on Friday.
By Ryan Lucas