Anthropogenic production of CO2and stratospheric ozone depleting chemicals is altering the plant growth environment. Numerous studies have examined the influence of increasing CO2and UV-B levels on plant growth and physiology, but few studies examine their interaction. Jack pine (PinusbanksianaLamb.), black spruce (Piceamariana(Mill.) B.S.R), and white spruce (Piceaglauca(Moench) Voss) were raised in growth rooms from seed for 16 weeks in air with either 350 or 700 μmol•mol−1of CO2in the presence or absence of supplemental UV-B irradiation. Classical and functional growth analyses were performed to identify treatment effects. Biomass production in all three species was increased by high CO2levels while UV-B light reduced it. Shade-intolerant jack pine showed a greater production of UV-B absorbing pigments in UV-B light than did shade-tolerant spruce species. Overall, white spruce was the most sensitive species to both treatment factors. The relative magnitude of the effects in the three species caused by enhanced CO2and UV-B levels indicate that future conifer seedling growth and competitive ability will be altered by the changing environment.