Zac Efron has opened up about his stint in rehab for cocaine and alcohol addiction.

The former Disney star, who is promoting his upcoming raunchy rom-com, That Awkward Moment, insisted that he had "never been this happy before" after tackling his demons last year.

During an appearance on the Today Show, the 26-year-old actor was caught off guard by Savannah Guthrie when she touched on his reported three-month stay in rehab in spring 2013.

"I know last year was a little bit hard. There were reports that you'd gone to rehab. Anything you want to share about that?" she asked. "I think mostly your fans just want to know how you're doing and that you're okay."

The 26-year-old replied, "I'm in the best place I've ever been. I've never been this happy before. I'm extraordinarily grateful for these guys and to be here promoting this movie. I don't know. Things are good. I don't know. Thank you for asking."

Reports first surfaced that Efron had spent time at a rehabilitation centre in September. The heartthrob later took to Twitter to thank fans for their support. "[It] means the world to me," he wrote.

"He's healthy, happy and not drinking. He's taking time to focus on working," a source also told E! News at the time.

Earlier this month, the High School Musical star admitted to People Magazine that he needed time away from the spotlight to work through some things.

"I learned so many things. So much," he said. "The best part of it was being able to reflect upon that experience and realise how much I have learned about myself and the kind of man I want to be."