Tax Year 2017: I paid for my mom's assisted living rent and care all of last year. Can I deduct it? If so, where?

If you are claiming her as a dependent on your tax return, you can claim some portion of her assisted living (for nursing services), but not her rent.  Then, it would be entered as medical expenses.

Who Can I Claim as a Dependent?

https://ttlc.intuit.com/replies/5187060

For medical expenses to be deducted on the tax return, you must itemize deductions on Schedule A, and your unreimbursed medical expenses must exceed 10 percent of your adjusted gross income (AGI).   Then, you can only deduct the amount by which your unreimbursed medical expenses exceed this 10 percent threshold (7.5% of AGI for age 65 and older until 2017). However, some states allow the full deduction, even if you don't have enough for your federal taxes.

Where do I enter my medical expenses?
https://ttlc.intuit.com/replies/4774888

Please see the following link for a comprehensive list of deductible medical expenses.  IRS Medical Expenses

I am running into the same issue. I can't find a place to enter the caregiver expenses. 

that is an old post..... you get the $500 tax credit for a dependent.  You can't take a deduction for any other expenses (I am assuming this is elderly care) unless they are disabled.