The 'Liz & Dick' actress - who agreed to plead no contest to two misdemeanor charges in relation to a car accident last summer in return for 90 days treatment in a residential clinic - will undergo her sixth attempt at getting sober when she begins her court ordered stint in rehab and her treatment will focus on her "large" alcohol consumption and reliance on legal medications.
A source told RadarOnline.com: "Lindsay will be treated for prescription drug and alcohol addiction during her stay.
"Lindsay's prescription drugs of choice are Adderall and Xanax, and in addition, she consumes large amounts of alcohol - specifically, vodka."
However, insiders are unsure how well the course of treatment will go as the 26-year-old star still doesn't think she has a problem and only agreed to go to rehab to avoid jail.
The source added: "The main problem when it comes to Lindsay ever getting sober is her absolute denial that she has any substance abuse issues. Once again, she is only going to rehab purely because it's a slightly more attractive alternative than going to jail. Of course, there is hope that once Lindsay is undergoing treatment she will recognise that she does in fact have a problem -- but given her history, it's very doubtful."
A spokesperson for the star - who also agreed to undergo 18 months of psychological counseling and 30 days of community service - said: "We do not comment on our clients' personal lives."