If I add my name to my Mother's deed (house) will I be able to claim the interest on my taxes?

You should check with your CPA on this to see what is able to be done.  Laws may differ from state to state and they will be the best ones to advise you if this is possible or not.

Jill is right on.  You should consult with a tax advisor on this one. 

Generally you will need to show that you are actually making the tax payments.  Simply adding your name doesn't fulfill the test.  The taxing agency will notify the IRS as to who made the payments.  They can easily cross check to determine if you were the responsible party.  Check with your CPA. 

You will want to check with your CPA or Tax Preparer but you can claim interest (or even just portions) without being on the title of the property. The IRS doesn't require deeded ownership to claim interest but they do look for who's actually paying. This is common with partners who own rental property, divorced couples or situations with multiple owners.

Also, interest deductions are generally only allowed for primary and secondary residences. If you don't live in the home you may have problems claiming the interest when it should be looked at like an investment property and handled under that section of the IRS tax code.

Short Answer, check with a CPA.

Happy New Year

In order to deduct home mortgage interest, the IRS requires that you be legally liable for the loan and that there be a true debtor-creditor relationship between you and the lender.  IRS Publication 936 specifically states, "You cannot deduct interest you pay for someone else if you are not legally liable to pay it."

In addition to the the standard "contact your CPA or tax adviser" suggestion/disclaimer, I think reading the relavent IRS Publication can be helpful.