The odorants of eight Japanese mainland native species (Citrus deliciosa, Zanthoxylum ailanthoides, Z. schinifolium, Z. piperitum, Phellodendron amurense, Orixa japonica, Skimmia japonica and Boenninghausenia albiflora), one tropical species (Euodia meliifolia), and one invasive species (Ruta graveolens) of the Rutaceae family, and three Japanese mainland native species (Angelica keiskei, Heracleum lanatum and Anthriscus sylvestris) and one invasive species (Foeniculum vulgare) of the Apiaceae family were analyzed using gas chromatography-mass spectrometry with dynamic headspace and thermal desorption methods. These species are host plants to Japanese Papilio butterflies. In this study, these 14 plants were classified into six major groups based on the odorant volatiles, which did not correspond to the current phylogenetic classification. Similarly, floral odorant analysis of the six plant species (Clerodendrum trichotomum, Cayratia japonica, Robinia pseudoacacia, Lonicera japonica, C. deliciosa and Z. ailanthoides) visited by Papilio butterflies for nectaring revealed the presence of linalool in all flowers. Floral volatiles in C. deliciosa and Z. ailanthoides exhibited a moderate resemblance to their respective leaf volatiles. Interestingly, the results obtained for C. trichotomum were not in complete agreement with those of previous reports, emphasizing the need for newer methods of extraction and analysis.