I just want to share my experience in filing my tax return. I'm a foreigner working in the United States. If your spouse and child/children are not in the U.S. and you want to claim them as your dependents for tax purposes, here's what I did:

1. Instead of filing my returns through mail, I visited the local IRS in my area.
2. If your spouse and child/children don't have an ITIN, then bring their original passports with you when going to the IRS office. This is for W7 application.
3. At first, I was told by an IRS employee that I cannot claim my spouse and child as my dependents because my country doesn't have any treaty with the U.S. I told them to get a copy of "tax guide for aliens" and I'll show them that I don't need any kind of treaty just to claim my spouse and child as my dependents.
4. DON'T always rely on the answer from the IRS customer service or their employees.

This is the rule:
If you are resident for tax purpose, then you can file resident tax return as Married Filing Jointly and claim your kids even if your spouse and kids are non residents.

Neither of the posts above is correct.

A dependent must be a citizen or resident of the US, or resident of Canada or Mexico.

Your spouse may be a non-resident but they would need to elect to be a resident in order for you to file MFJ.

Please read page 26 of Publication 17; col. 1 Adobted child, col. 2, Child's place of residence.
If you legally adopt a child (foreign child), this test is met... Children usually are citizen or residents of...

Please read page 26 of Publication 17; col. 1 Adobted child, col. 2, Child's place of residence.
If you legally adopt a child (foreign child), this test is met... Children usually are citizen or residents of ...

MukatA, the example you are quoting relates to a specific instance where a US citizen adopts a foreign child. It does not fit with the example provided by the OP.