Talk show host David Letterman has apologised to Paris Hilton in her latest appearance on his show.

The 26-year-old socialite's latest appearance on the Late Show with David Letterman was completely in contrast to her last, when the CBS host was constantly picking her about her just-finished jail sentence.

However, Letterman seemed to regret his earlier behaviour on the show with the reality star. He even explained the reason behind his previous behaviour with Hilton.

"We have a lovely woman who's been in prison. I put those two things together and my head starts spinning," People quoted Letterman, as explaining.

He recalled the last show and kept regretting his verbal confrontation with Hilton, even though she claimed she was finished talking about her time in jail.

"I continued to press the point. I thought I was hilarious," recalled Letterman, until he was told the next day, "No, you were an ass----."

When he heard that the multimillionaires was hurt and vowed not to return on the show, he called her, wrote a letter and sent flowers.

Hilton called the gesture "sweet' as Letterman persuaded her to return on his show, just before her new movie, The Hottie and the Nottie, opens.

"It's like a first date," said Letterman, admitting he was "on probation."