Even though terpene emissions of boreal needle trees have been studied quite intensively, there is less knowledge of the emissions of broadleaved deciduous trees and emissions of larger terpenes and oxygenated volatile organic compounds. Here we studied downy birch (Betula pubescens) emissions, and especially sesquiterpene and oxygenated sesquiterpene emissions were found to be high. These emissions may have significant effects on secondary organic aerosol formation in boreal areas.