The great genetic and phenotypic diversities characterize the mandarin species (Citrus reticulata). The present study aimed to evaluate a part of this diversity with molecular markers and through the composition of leaf (LEO) and fruit peel (PEO) essential oils. Seventy-two cultivars were chosen for this study to represent some wild and cultivated mandarins growing in the same orchards. The essential oils were analyzed via gas chromatography (retention indices) and via gas chromatography coupled with mass spectrometry. The low similarity of `Tachibana' and `Korail tachibana' with mandarins and other species suggested that they were pure mandarins but were not involved in the genesis of the cultivated forms. This distinction was also evident at the aromatic level with specific compounds or unusual proportions, such as delta-3-carene in PEO or beta-phellandrene at 24.9% in `Korail tachibana' LEO. `Kunembo' and `Ben di gang ju' were genetically and chemically identical, with a high proportion of myrcene (>20%) in their LEO. In general, the genetic diversity of SSR markers was higher than the chemical diversity. From the 72 accessions, 54 genotypes were identified, with only 8 aromatic profiles in PEO and 9 in LEO. This diversity of essential oils of mandarins offers new perspectives for the research and validation of new aromatic properties for food and cosmetic purposes.