The 'Pearl Harbor' actor says becoming a father to two-year-old Violet, his daughter with wife Jennifer Garner, was the catalyst he needed to overcome his habit.
Once he had made up his mind to quit, Ben decided to take a leaf out of pal Matt Damon's book by visiting a hypnotist.
He told Oprah Winfrey: "I finally decided to quit smoking when I found out I was going to have a child. That was the thing that sort of put it over the top for me. I decided to go to a hypnotist. You sit in a chair and the hypnotist sips water and just talks to you for an hour, and explains how nicotine is poison.
"All of a sudden, I thought, 'This is asinine that I've been doing this to myself for all these years.' My last cigarette was on November 10th, 2005, and I feel a huge difference in my health now that I don't smoke. I feel like I'm in better shape than I was five years ago."
Source: People