Robert Downey Jr's father is more proud of him for beating his drug addiction rather than his acting success.

Robert Downey Sr's achievements are to be celebrated by his 'Iron Man' star son and 'Inherent Vice' director Paul Thomas Anderson at a fundraiser this weekend but he's revealed his proudest moment was seeing his son overcome his addictions.

He told the New York Post newspaper's PageSix column his ultimate career ''highlight'' was ''when my son turned his life around [from drug problems], that's my highlight moment''.

The 'Hugo Pool' filmmaker is being honoured at the Friends of Cinefamily weekend fundraiser and retrospective in Los Angeles that will include a Q&A session with his son, which he admits will likely be ''embarrassing'' because they joke around so much.

Downey Sr. recalled: ''Right after 'Iron Man', he was voted on of the Time Magazine 100. He called me up and asked me to get in a tuxedo. So I rented a tuxedo, [but] he didn't like the way I had the tuxedo.''

Explaining how he got his own back on his son after he thanked him for being ''his mentor'' on stage, he continued: '''What do you have to say dad?' - I said, 'I'm not your father.' ''

And Downey Sr. also confessed he's looking forward to seeing his new granddaughter, Avri Roel Downey - whom Downey Jr. and wife Susan welcomed into the world earlier this month.

He added: ''The most exciting part of going to LA (is) I get to see my two-week-old granddaughter.''