Carotenoids are major secondary compounds in Citrus determining the color of fruit and nutritional values. Carotenoids are isoprenoic compounds, and function as color pigments in the flower and fruit to attract pollinators and seed-dispersing animal and chromophore for light harvest and photoprotectant during photosynthesis. In the aim of developing new cultivars with high value using molecular breeding technology, we had performed screening of flesh and peel specific genes by differentially expressed gene screening in Citrus unshiu fruits. From the screening, carotenoid isomerase (CRTISO)1, which converts pro-lycopene to all-trans-lycopene, was identified as peel-specifically expressed gene. In this study, the gene encoding the CRTISO1 was cloned, sequenced, and compared to the CRTISOs in other plant species. Comparison of the cds sequence to other plant species revealed 75% and 78% identity with CRTISO1 of Zea maize and CRTISO2 of Arabidopsis thaliana respectively. We also cloned CRTISO2 from C. unshiu which declines the expression while maturation (Kato et al., 2004), and the gene structure was analyzed. This is the first work reporting the full sequence and gene structure of CRTISOs in C. unshiu, and would give important information in understanding the carotenoid synthesis in the Citrus fruit.