Lindsay Lohan and David Letterman

It's the question on everyone's minds: Isn't Lindsay Lohan supposed to be in rehab?

Instead, the troubled 26-year-old actress pops up on the Late Show with David Letterman Tuesday — her first appearance on the show since 2007 — and things go less than smoothly.

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After first chiding Letterman for not reading up on her latest updates in the tabloids, Lohan clarifies that she begins her three-month, court-ordered stint in rehab on May 2. He then grills Lohan about how many times she's been in rehab — "several," she replies — and what exactly she will be "rehabbing" and working on improving?

"We didn't discuss this in the pre-interview," a wary Lohan tells the studio audience. "I think I'm the happiest when I'm working, and the healthiest, and 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. It's a blessing."

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When asked if she has addiction problems, a visibly peeved Lohan tells Letterman, "Now you sound like Dr. Phil." He then probes further and asks if she drinks too much, to which Lohan curtly responds that they've already discussed that subject in the past. "See, I'm the one who's having the blackouts," Letterman awkwardly jokes. "I ought to be in rehab."

Watch the full interview here:

Late Show with David Letterman airs weeknights at 11:35/10:35c on CBS. Will you be tuning in to see Lohan's full sit-down?

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