Ali Lohan showed off her pencil-thin figure in Hawaii Friday.

The 17-year-old model is on the island of Oahu with big sis Lindsay, and was spotted in super-short cut-off jeans and a midriff-baring tank top.

As RadarOnline.com previously reported, Lindsay was invited to attend the Pipeline Masters surfing competition where her friend Any Irons was being honored. Irons was a legendary pro surfer who died of a drug overdose last year.

After watching some of the competition, the Lohan girls walked to a nearby convenience store for refreshments, but not before Ali playfully sent a karate-like kick in the direction of a friend.

PHOTOS: Scary Skinny Ali Lohan Visits Hawaii With Lindsay

Earlier in the week, Ali attended a casting call in Beverly Hills where Us magazine described her as "alarmingly gaunt and pale -- with noticeably stick-thin arms and legs."

Ali, who towers over Lindsay, turns 18 December 22. She so far hasn't commented on Lindsay's Playboy pictorial which was leaked on the Internet on Friday.

PHOTOS: Lindsay Lohan Surfs Away From Playboy Controversy In Hawaii

Lindsay Lohan's nude pictorial in Playboy has already been leaked but for those of you who buy Playboy for the articles, RadarOnline.com has a sneak peek of what the model/actress told the mag.

“Sex and sexuality are a part of nature, and I go along with nature," Linds said.

"I think Marilyn Monroe once said that. I certainly agree with her…Knowing yourself and your body is so important because it gives you confidence, and in life, women need confidence. It’s a very male-dominated world to begin with, so knowing yourself and being comfortable with your body is an important thing for me as a woman.

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"Everyone is entitled to their opinion, but this is mine.”

As RadarOnline.com has been reporting, all of the nude pics from the pictorial -- that show Lohan channeling Monroe for the shoot -- were leaked to the Internet on Friday, a full week in advance of the magazine hitting the stands.

LiLo is now is now in Hawaii with her sister Ali. The nude cover girl was invited to attend the Pipeline Masters surfing competition, which this year honored a surfer friend of Lindsay who died from a drug overdose.

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She's expected back in Los Angeles on Monday, the same day Playboy tells us they'll be releasing the one pic from the shoot where Lindsay is dressed.

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