The currency in Cambodia is ”Riel” but you will see US dollar on most of the price lists and menus.

Make sure you have small bills because some places only have riel to give you back in change, and 20 US will give you 80.000 Reil, so bring a bag when you buying a pack of cigarettes with a twenty….

If you want to exchange cash don't go to the bank go to the Market place
(se Map) because the exchange people will give you better exchange rate than the bank, and they are not hard to spot (they stand in front of a big glass box full of different currency's.

In Cambodia there are no ATM machines. Travelers may get a cash advance on their Visa or Master Card at all major banks at little or no commission and also at some shops, but they will charge high commission. Travelers Cheques (TC)  - You can exchange TC at any bank in Cambodia , but you have to pay about 2-4% commission for converting it into U$ dollars.