The volatile emissions of black spruce (Picea mariana(Mill.) BSP) seed cones still attached to a live 7 m tall tree (in situ) were compared with those of cones from the same tree that had been severed (ex situ). Volatiles were collected simultaneously with a manifold headspace sampling system, adsorbed on Porapak®Q, and the extracts analysed by capillary gas chromatography (GC) and GC - mass spectrometry. The relative abundance of the identified constituents, tricyclene, alpha- and beta-pinene, camphene, sabinene, beta-myrcene, DELTA-3-carene,p-cymene, beta-phellandrene, limonene, gamma-terpinene, alpha-terpinolene, camphor, borneol, and bornyl acetate differed quantitatively, almost qualitatively, between in situ and ex situ samples. For example, camphene and bornyl acetate represented ca. 7% and 12% of total emissions, respectively, of the volatiles from in situ cones and ca. 0.9% and <0.2%, respectively, of the volatiles from ex situ cones. beta-phellandrene and beta-pinene were consistently less abundant in extracts of in situ collections (ca. 4.5% and 22%, respectively) than in those of ex situ collections (ca. 6% and 32%, respectively). Also, the release rate of total monoterpenes from in situ seed cones was approximately twice as high as that from ex situ cones. These results indicate that ex situ sampling does not accurately depict the composition of volatile emissions by seed cones and suggest that tests for biological activity based on such compositions could lead to erroneous conclusions.