Opposition Leader Malcolm Turnbull made these admissions when he appeared last night on Q&A on the ABC.

Mr Turnbull, who is serving his second term as an MP, was elected Opposition Leader last week.

On Q&A last night, Mr Turnbull was peppered with questions about his character and personal wealth.

''I am who I am,'' Mr Turnbull said. He was asked if he was arrogant, had an inflated ego or was a cross between Napoleon and Winston Churchill as suggested by Word Vision Australia chief executive Tim Costello.

Mr Turnbull joked, ''Short and fat? It's rather unkind when you think about it.''

The newly minted leader also quipped that the other Costello, former treasurer Peter, ''has always got a good word for me''.

Mr Turnbull identified his differences with former prime minister John Howard, saying he was born in a different era, supported the apology to the Stolen Generations, was a committed republican and backed signing the Kyoto Protocol.

He opposed legal discrimination against same-sex couples but believed marriage should be between a man and a woman.

Mr Turnbull declared, ''Yes, I've smoked pot, but it was a mistake to do so.'' Q&A host Tony Jones suggested he could be the first Liberal leader to admit it.

The Opposition Leader's personal hero was his late father, Bruce, ''who never said a bad thing about my mother after she left''.

Mr Turnbull often described as the richest man in Federal Parliament argued people should be judged by what was in their hearts rather than their pocket.

He had been asked whether he thought his personal wealth affected his decisions and hampered his ability to relate to average Australians.

''In a nutshell, if you want to boil it all down, I believe that the role of government is to enable people to do their best,'' he said.

''I believe government is there to enable us to exercise our freedom, to do so in a fair society.

''Whereas I think [Prime Minister Kevin] Rudd has a different view a view that is perhaps more bureaucratic, that sees government as knowing best.''