AbstractGas chromatography–mass spectrometry (GC–MS) and gas chromatography–olfactometry (GC–O) were used to study aroma‐active compounds in extracts of American, French, Hungarian and Russian oak woods. Compounds that presented high odour intensities for the non‐toasted oak woods were guaiacol, hexanal, trans‐2‐nonenal, trans‐oak lactone, cis‐oak lactone, eugenol, vanillin and trans‐isoeugenol, whilst the same compounds, in addition to furfural, 4‐methylguaiacol and cis‐isoeugenol, proved important in the toasted oaks. Like the oak lactones, cis‐ and trans‐isoeugenol presented woody/oak odours, particularly in the toasted samples. For Hungarian and Russian samples, both characterized by their lower content of oak lactones, trans‐ and cis‐isoeugenol presented higher odour intensities. For this reason, samples of low oak lactone concentrations, such as Hungarian and Russian oak woods, but also containing isoeugenols, can impart woody/oak odours to wines. Copyright © 2008 John Wiley & Sons, Ltd.