In mid-September, Finavia (formerly known as the Civil Aviation Administration) will start work on an enlargement of the airport's international terminal and a new luggage processing centre.
Most of the expansion is aimed at traffic to and from East Asia, which is an area of strong growth for the national air carrier Finnair. The work is scheduled to last about three years.
The estimated price tag for the upgrade is 143 million euros, making it the aviation agency's biggest investment ever.
When the project is completed, Helsinki-Vantaa will have eight passenger bridges for wide-bodied aircraft, up from the current five. Only two of the present bridges are large enough for the new Airbus A340 and 350 jets that Finnair is buying.
The baggage centre will be located in a new three-storey building. The airport operator says the expansion will enable it to handle 15 million passengers a year, up from 11.5 million now.
Some 30 airlines use Helsinki-Vantaa Airport, with service to and from 110 destinations around the globe.