Our grandson lives with us but we do not have custody of him. His mother receives food stamps and occasionaly buys food for us. He is also on medicaid. She is not going to claim him because she did not work in 2009. Are we able to claim him as a dependent?

Yes, as long as you provided at least half the child's support for the year (and assuming he is under age 19, or age 24 if a full-time student). You don't mention the father - are you sure that he can't (or won't) claim the child as his dependent?

He will not be filing taxes either because he did not work in 2009. Thanks for the info