Are there any problems crossing Kosovo's international borders or having their stamp in your passport?

Going from Romania into Serbia, then into Kosovo and on to Albania should be no problem at all.

The only problematic situation I know of is moving from a third country into Kosovo and then into Serbia and finally leave to another country. This is because when entering Serbia through Kosovo you don't get a Serbian entry stamp and therefor have not entered legally.

Some friends of mine did exactly that and when they left Serbia for Hungary the immigration officials just crossed out the Kosovo stamp.

When travelling from Serbia into Kosovo you usually don't get a Kosovo entry stamp but you may get a Kosovo exit stamp when you leave.

I have entry stamps but no corresponding exit stamps for several Balkan countries including Serbia.

I went to Kosovo 4 times in 2011, got two stamps 3 times, once they forgot one. Serbians are not so good with stamping, I didn't get one when leaving to Bulgaria. That means that you can just ask the Kosovars not to stamp your passport when you leave Kosovo once you entered it from Serbia.

What is important to remember is that entering Serbia from Kosovo after entering the latter from a 3rd country may prove impossible or problematic. I read an account of a Polish cyclist who was refused entry to Serbia although some German cyclists in front of him were allowed to enter. Afterwards, he was smuggled in by Polish peacekeeping soldiers through a green border into Serbia :) I met those same soldiers one day in Macedonia when they were on a weekend off and they confirmed this story.

So... even when you are refused entry to Serbia after entering Kosovo from a third country, you still stand a chance if you meet Polish KFOR! ;-)

Bumping old post:

Having Kosovar stamps is not a Problem: however, if using a passport, you cannot enter Kosovo from Montenegro or Macedonia, or by air, and then continue to Serbia - you can only travel from Serbia to Kosovo and then back.

To be exact: on the way from Kosovo to Serbia, there will be one Kosovar exit check, and then a Serbian entry check. The Serbians will then refuse you entry if you don't have a current Serbian entry stamp (which is only possible if you entered Serbia from a third country and then went to Kosovo)

There is one way around this rule, though it's only possible for (most) European nationals: using an ID card instead of a passport. They cannot be stamped, so the Serbs cannot prove how you entered Kosovo.

However, the ID card must be one accepted for entry to Serbia, i.e. from an EU country, Bosnia, Macedonia, Montenegro or Switzerland (or, of course, Serbia or Kosovo)

Bosnian ID cards are valid for Serbia but not for Kosovo so Bosnian citizens must be careful to use the passport for the Kosovar check, and the ID card for the Serbian check

I traveled to Serbia and then Macedonia before going to Kosovo. I was on a bus from Kosovo to Bosnia. Serbia did not like my Kosovo passport stamp. Another passenger asked them to please let me and my two kids into Serbia.

It was a dark night and I could see a tank. I was so very scared. I am so happy they did let me in. Good luck to all other travelers.