By Plane--The Helsinki-Vantaa Airport (tel. 09/827-71) is 19km (12 miles) north of the center of town, about a 30-minute bus ride. Special buses to the airport leave from the City Terminal at Asemaukio 3, and stop at the Air Terminal at Töölönkatu 21 (near the Scandic Hotel Continental) at 15- to 30-minute intervals every day between 5am and midnight. Tickets cost 4.90€ each way. A slightly less expensive, but also less comfortable, option is taking public bus no. 615, which departs from Railway Square (Platform 12) two or three times an hour between 5:30am and 10:20pm. The price is 3€ each way.
A conventional taxi ride from the airport to the center of Helsinki costs about 20€ to 25€ each way; you'll be assured of a private car shared only by members of your immediate party. A slightly cheaper alternative is to hire a special yellow taxi (tel. 09/220-025-00) at the airport terminal, which might be shared by up to four separate travelers; the cost is 18€ per person.
On your departure, note that the airport requires passengers on domestic flights within Finland to check in 30 minutes before flight time. Passengers on flights to other points in Europe usually must check in between 45 and 60 minutes before takeoff, and passengers bound for any of the former regions of the Soviet Union or anywhere in North America usually need to check in between 1 and 2 hours in advance.