Car rental in Greece?

http://www.autoeurope.com/

You don't supply much information, but a few things come to mind to be aware of to rent one way in or out of Greece. International drop offs will have very high fees, if allowed at all. Factor that into your costs and confirm you can do it. Greece is surrounded by countries that might be on "no travel" zones for rental cars. Be sure to confirm that wherever you rent from will allow you to drive in the countries you want/need to. If you do rent, be sure to purchase the super CDW coverage. It is highly unlikely your own insurance or credit card will cover you. Greece requires an International Drivers Permit (available from AAA in the US). Be sure to get it before your trip.

Thanks for responding, first of all.. Our plan was original drive through Bulgaria and Croatia but like you said some countries are in the no drive zone and, so we decided to drive through Italy which means we would have to take a ferry. We still seem to have problems planning;
Greece does not allow international one way - at least as far as I've been able to understand. One way rentals in Greece from a city to another - which was an alternative - driving and dropping the car where the ferry is are also about 500% more expensive than a regular rent. We were asked to pay over 300 Euro per day for an Economy class car. One way international car rental in Italy to France is also still overcharged. I've read about people who have driven different cars in different countries to avoid the one way charges, which means that if its possible, we would drop the car at one side of the border and use public transportation to the other side and then continue with another car. My question is, I am sure I am not the first one to plan a trip to Europe where you pick up a car and drop it off somewhere else.. whether its rental or not .. is there no way around it ?? Avis, Hertz and other "big" companies treated me like I'm the first one to ask about something like that and completely got lost trying to work out a price. As if I asked to rent a car on the moon and drop it off on mars..

Also, if It is possible of course, we would rather have the same car - it convenient , and we carry some luggage that might be a problem on a t rain: a pet, and some households.

For such an extensive car trip through Europe, most people lease a car. I've known people that have done the lease-purchase option and the car is shipped home afterwards but I don't know options for just leasing. As you have found, the fees for one-way drop offs from rental agencies are very high. Autoeurope that was suggested may be more helpful for your circumstance than others.

Getting a pet through some borders may be difficult, have you checked that out? I know some trains allow small caged pets( dogs and cats etc) but they have to be small and in a carrier.

I would highly recommend that you go to Gemut.com to research some of the issues you will face. Then call them. They are experts in all this and can set you straight on the rental car rules and regs that most of us can only speculate about. They are actually in OR, so there's a 3-hour time difference for you.