The actor, who plays United States founding father Adams in the two part historical epic, blames co-star Tom Wilkinson for tempting him to pick up cigarettes again in between takes.
He says, "I'd had enough. It was a tough job. John Hancock was on the phone to his agent... and Ben Franklin (Wilkinson) was having a Marlboro Light.
"So I said, `Give a founding father a cigarette. This revolution is killing me.' It was a very tough time."
Giamatti is planning to take up yoga to help him quit: "It helped me quit smoking before. So it may help me again."
Source: WENN