01/18/2013 09:36 pm ET Updated Jan 18, 2013

Lance Armstrong And Oprah Discuss The Moment He Told His Son The Truth (VIDEO)

In part one of his no-holds-barred interview with Oprah Winfrey, Lance Armstrong admitted to using banned substances to enhance his cycling performance.

"Oprah and Lance Armstrong: The Worldwide Exclusive" continues January 18 on OWN and Oprah.com. In this clip, Armstrong talks to Oprah about the moment he told his 13-year-old son, Luke, the truth.

"When this all really started," Armstrong says, "I saw my son defending me and saying, 'That's not true. What you're saying about my dad is not true....' That's when I knew I had to tell him. And he'd never asked me. He'd never said, 'Dad, is this true?' He trusted me."

Part two of Oprah's interview with Lance Armstrong aired Friday, Jan. 18, starting at 9 p.m. ET on OWN. The interview was simultaneously streamed LIVE worldwide on Oprah.com.



PHOTOS: Lance Armstrong