The currency of Liechtenstein is the Swiss Franc (CHF).
Though they take Euros in most places, they often have special exchange rates. And if you don’t have the exact amount, you will get your change in Swiss Francs - so don’t give bank notes, or ask first. It’s recommended to first exchange some money to Swiss Francs or get Swiss Francs from one of the cash machines, which you will find in every village.
ATMs / cash machines
ATMs are available in all parts of Liechtenstein, in banks, supermarkets, post offices and elsewhere. As a foreign card is inserted into the machine, you will most likely be offered a good choice of languages – no need to navigate through german-language menus! The exchange rate you'll receive will be fairly good (the actual/current index), and there may only be a small service charge, which depends on your bank back home.
Photo: optimal-banking.de / Schweizer Franken