Nanocomposites with ZnSn(OH)(6) (ZHS) and ZnO have been synthesized by a hydrothermal approach. Both of sputtering and dip-coating methods were used to deposit different ZnO seed layers on silicon substrates. After a hydrothermal process, the synthesized ZnO nanorods became an aligned or a flower-like structure. Then the ZHS microcubes were decorated on the various ZnO nanorods to form the high surface-to-volume ratio sensing nanocomposites. The prepared n-type nanocomposites on p-type Si substrate are used to detect carbon dioxide gas by measuring its current-voltage characteristics changes. Comparison of both structures, the flower-like sample has a better response of 354% to 2500 ppm CO2 at 150 degrees C. It also has a shorter response time of 10 s and can be used as a high performance CO2 sensor.