Sober Robert Downey Jr. Back on Big Screen

N E W   Y O R K, Oct. 10 -- After struggling for years with drug addiction, Robert Downey Jr. says he truly believes temptation will no longer get the best of him.

Downey told ABCNEWS' Diane Sawyer his life is no longer an everyday struggle because he finally made a decision to get off drugs for good.

"I know there's all the stuff about it's a disease, it's a moral dilemma … but I think at the end of the day, it's the lack of making a solid personal decision. Sometimes the stakes have to be so high that it's clear," Downey said on Good Morning America.

During the filming of his first movie in three years, The Singing Detective, the award-winning actor says he was clean and sober throughout production.

The Singing Detective — Downey's first film since his release from jail and subsequent treatment in a live-in drug rehabilitation facility — is a big screen version of a six-part British television miniseries which was a hit on PBS.

The show revolved around a private investigator who doubled as a singer in a dance band.

For the movie, the story has been reset in Los Angeles and moved from the 1940s to the 1950s.

Downey struggled with drug addiction for years before he was finally sentenced to three years in prison back in 1999. A Los Angeles Superior Court judge handed down the sentence after the actor violated his probation on a 1996 cocaine possession charge by repeatedly missing mandatory drug tests.

After his release in August of 2000, Downey was arrested just three months later on Thanksgiving after police in Palm Springs caught him with cocaine and methamphetamine.

Then, just five months later, he was arrested again and charged with a misdemeanor count of being under the influence of a controlled substance. The actor immediately checked himself into a rehabilitation facility for one year of treatment.

Downey says rehab only works if people are prepared to fully embrace it, and he says he finally came to that point in his life.

Downey had been working on Fox's Ally McBeal before his last arrest. When the news broke, producers dropped Downey, who had won a Golden Globe award and Screen Actors Guild trophy for his role on the show.