All plants are able to emit volatile organic compounds (VOCs) and the content and composition of these molecules show both genotypic variation and phenotypic plasticity. VOCs are involved in plant–plant interactions and for the attraction of pollinating and predatory insects. The biochemistry and molecular biology of plant VOCs is vast and complex, including several biochemical pathways and hundreds of genes. In this review the site of synthesis, the biosynthesis and the functional role of VOCs are discussed.