Is it not true that they need to be either green card holders or citizens in order for them to satisfy the criteria ?
Refer to this answer given by Rajiv Khanna:
Q23 My parents are in the U.S on Visiting Visa. Recently I heard that I can claim them as my dependents while filing tax returns. Is it true?
A23 Your parents may be your dependent while visiting you on temporary visa, but you may not be able to claim as your dependent on your tax return.
To claim an exemption for a dependent, all of the following tests should be met;
1. Member of Household or Relationship Test
To meet this test, a person must either:
Live with you for the entire year as a member of your household, or Be related to you as parents, brothers, sisters, children etc.
2. Citizen or Resident Test
To meet the citizen or resident test, a person must be a U.S. citizen or resident, or a resident of Canada or Mexico, for some part of the calendar year in which your tax year begins.
3. Joint Return Test
Even if the other dependency tests are met, you are generally not allowed an exemption for your dependent if he or she files a joint return.
4. Gross Income Test
Generally, you cannot take an exemption for a dependent if that person had gross income of $2,900 or more for 2001.
5. Support Test
Generally, you must provide more than half of a person's total support during the calendar year to meet the support test.
I think in your case some of the tests may be met but not all, particulary the Resident Test.
Further, to claim an exemption for a dependent (parents in your case) on your tax return, you must list either the social security number (SSN) or individual taxpayer identification number (ITIN) for the dependent.
[Index] [Compiled by Law Offices of Rajiv S Khanna]