The relaxation dynamic of ribose and deoxyribose water solutions at different concentrations has been studied by broadband dielectric spectroscopy and differential scanning calorimetry in the temperature range of 150–250 K. Two relaxation processes are observed for all the hydration levels; the slower (process I) is related to the relaxation of the whole solution whereas the faster one (process II) is associated with the reorientation of water molecules in the mixture. As for other polymeric water solutions, dielectric data for process II indicate the existence of a critical water concentration above which water mobility is less restricted. According to these results, attenuated total reflectance Fourier transform infrared spectroscopy measurements of the same sugar solutions showed an increment in the intensity of the OH stretching sub-band close to 3200 cm−1 as water content increases.