Finland joined the Euro area in 2002. Credit and debit cards are frequently used in almost all occasions even when paying small amount of fees.
If you are coming to Finland for a longer visit, not just travelling, you need to open a bank account. When you open a bank account, you will be asked for your Finnish social security number. Prior to this getting a residence permit is recommended. Do not forget to take your ID or passport with you when you need to deal with legal issues such as opening a bank account. Every bank has different requirements and offers for students and foreigners. In the related links part you will find Finnish bank links.
There is usually at least one ATM in every city and town. There is a yellow sign with the word "Otto" above the ATM. Usually you can find it close to the bank. Notice that the smallest amount you can get from the ATM is 20 euros.
From the related links you will find a link to a Finnish website "Missä Otto?" ("Where is Otto?"). Type in the city or town you're in, and the system will find the ATMs in that area.
Photos: Youth Information Centre Nappi