South Korean rapper Psy never got the chance to say goodbye to his late grandfather because the Gangnam Style hitmaker was behind bars when he took his last breath.

Psy reveals he was arrested for smoking and possessing marijuana a decade ago in 2002.

He tells America's Star magazine, "I smoked something that my country strictly prohibits. I didn't realise I was doing something wrong until I got arrested... To tell you the truth, I was 25 years old back then, and I was scared as hell."

And his parents refused to bail him out.

He says, "My mother said, 'I knew you were going to cause trouble!' Then she left. My father shook my hand and said, 'Take this opportunity to quit smoking cigarettes.' Then he left too."

But while the sensation remained in custody, his grandpa lost his battle with cancer, forcing Psy to skip out on his funeral - and he regrets it to this day.

He adds, "I was very close to him. I was not there at the funeral... I will regret this for the rest of my life, because my grandpa loved me so much and I couldn't be there for him when he was on his deathbed."