The Mean Girls star failed to show for a hearing related to her ongoing court battle with photographer Grigor Balyan, who claims he ended up in hospital after he was hit by Lohan's car outside a nightclub in 2010.
Lohan, who has just returned to the U.S. from a promotional trip to Brazil, later popped up outside the Ed Sullivan Theatre, where Letterman tapes his nightly show.
And while Balyan's lawyers are reportedly in the process of filing papers demanding a judge force Lohan to show up for her next day in court, the actress appeared to be far from concerned about her legal issues.
Tweeting after her chat with Letterman, she posted: "Had a wonderful time at the @Late_Show. It was great fun!"
In her first Tv interview since November (12), Lohan discussed her upcoming rehab stint with Letterman, stating, "I think this is an opportunity for me to focus on what I love in life and I don't think it's a bad thing. I think it's a blessing."
Lohan must begin three months of court-mandated rehab by 2 May (13) as part of a plea deal stuck in March (13).
She appeared on The Late Show to promote her guest starring role on Charlie Sheen's sitcom Anger Management.