My father is in a nursing home and I pay for the entire cost. Can I deduct the expenses on my tax return?
You may deduct qualified medical expenses you pay for yourself, your spouse, and your dependents, including a person you claim as a dependent under a Multiple Support Agreement. You can also deduct medical expenses you paid for someone who would have qualified as your dependent for the purpose of taking personal exemptions except that the person did not meet the gross income or joint return test.
Nursing home expenses are allowable as medical expenses in certain instances. If you, your spouse, or your dependent is in a nursing home, and the primary reason for being there is for medical care, the entire cost, including meals and lodging, is a medical expense. If the individual is in the home mainly for personal reasons, then only the cost of the actual medical care is a medical expense, and the cost of the meals and lodging is not deductible.
You deduct medical expenses on Form 1040 Schedule A (PDF), Itemized Deductions. The total of all allowable medical expenses must be reduced by 7.5% of your Adjusted Gross Income.
For more information, refer Publication 502, Medical and Dental Expenses.

What if you pay medical expenses of a deceased spouse or dependent?
 If you paid medical expenses for your deceased spouse or dependent, include them as medical expenses on your Form 1040 in the year paid, whether they are paid before or after the decedent's death. The expenses can be included if the person was your spouse or dependent either at the time the medical services were provided or at the time you paid the expenses.

What if the decedent's return had been filed and the medical expenses were not included?  
Form 1040X can be filed for the year or years the expenses are treated as paid, unless the period for filing an amended return for that year has passed. Generally, an amended return must be filed within 3 years of the date the original return was filed, or within 2 years from the time the tax was paid, whichever date is later.
Example:
John properly filed his 2004 income tax return. He died in 2008 with unpaid medical expenses of $1,500 from 2004 and $1,800 in 2008. His survivor or personal representative can file an amended return for 2004 claiming a deduction based on the $1,500 medical expenses. The $1,800 of medical expenses from 2008 can be included on the decedent's final return for 2008.

Medical Expenses for Non-dependents
You can deduct medical expenses for non-dependents, if the only reason you cannot claim him as a dependent is because his gross income is $3,200 or more, or because he filed a joint return. However, all of the other rules for dependents must be met.

If you are divorced or separated, you can include amounts you paid for your child's medical care even though the other parent claims an exemption for this child under the divorced or separated parents' rules.

If you are considered to have provided more than half a person's support under a multiple support agreement (and no one alone provides more than half) then you can include medical expenses YOU paid for that person. This is true even if you cannot claim the person as a dependent because he or she had a gross income of $3,200 or more, or filed a joint return.

You can include medical expenses you paid for an ADOPTED child who qualifies as your dependent. If you incurred medical expenses prior to adoption, those amounts may be included as long as the child qualified as your dependent when services were provided or when expenses were paid.