He faced a number of questions from reporters today about an interview in which he admitted to having smoked up as recently as three years ago, when he was already a member of Parliament.
Trudeau expressed no regrets.
"No, it wasn't a mistake,'' Trudeau said in response to a question in Quebec City.
"I do not consume cannabis. I am not a big consumer at all. I tried it...
"I've never tried other types of hard drugs. I am not a consumer of marijuana but, yes, I've already tried it. I used it - maybe five or six times in my life.''
He said he believes public opinion has moved on and he's confident that Canadians will judge him less harshly than his political opponents.
What matters now, Trudeau said, is ending a marijuana prohibition policy that he says costs law enforcement $500 million and has left hundreds of thousands of people with criminal records since the Conservatives took office in 2006.
He has said that issue touched his own family.
Trudeau originally made the marijuana admission in a candid interview with the Huffington Post, in which he also revealed that his youngest brother, Michel, was charged with marijuana possession shortly before his 1998 death in an avalanche.
He said he's smoked pot only five or six times in his life, it's never done much for him and he no longer indulges.
Trudeau's admission will doubtless give more fodder to the Conservatives, who've been pointing to his support for legalizing and regulating marijuana as evidence that he doesn't have the judgment to be prime minister.
Prime Minister Stephen Harper says Trudeau's actions "speak for themselves.''
But Trudeau was unrepentant, joking on Twitter that he made a mistake in being so open and is now coming under "vicious attacks'' for the Huffington Post interview - over his other admission that he doesn't drink coffee.
© 2013 The Canadian Press