The Croatian currency is called Kuna.
 
Opening a bank account in Croatia is not difficult and can be done at any major bank. You will need a passport or an EU National ID card, and funds to deposit.

If you wish to have an ATM card and to access Internet Banking Services, you will need to show proof of residency in Croatia, such as a Long-Term Visa and a lease. A utility bill will also help prove the residency.

English or German-speaking staff is available at most banks.   Generally, banks are open for business Monday to Friday from 8:00 AM until 7:00 PM. Some branches may be open on Saturday mornings.

The customer can immediately access funds with a check drawn against the account once an account is opened, but will only be able to withdraw them from an ATM machine when an ATM card has been issued, which usually takes from one to two weeks.

There are no restrictions on the importation or exportation of foreign currency into the Republic of Croatia. However, the importation and exportation of Croatian currency is restricted and regulated by the Croatian National Bank. Their web address is: http://www.hnb.hr/eindex.htm

When you are shopping in Croatia you cannot pay for your items in traveler’s checks or Eurocheques.  They must first be exchanged for Croatian kunas.  If you do travel with these items, you can exchange them at international banks and travel agencies, exchange offices and post offices. Fees can be large for cashing these checks, so always ask the fee up front.

A word of advice if you are traveling with these checks is to get large denominations.  The fewer you have to cash, the less in fees you will have to pay.  Your passport is required to cash them.

Shop around.  Banks in Croatia vary their exchange rates and you will need to find the most favorable.
 
When you use your Credit or Debit Card, the bank will use the current exchange rate when they convert to the Croatian currency.  ATMs are throughout Croatia.