A technique for measuring moisture concentration profiles based on scanning neutron radiography is presented. With this technique moisture concentration profiles have been measured during drying of brick and kaolin clay. The isothermal moisture diffusivity as a function of moisture content could be determined directly from these profiles. An error analysis shows that the minimum spatial resolution for scanning should be 0.5 mm. If this condition is not satisfied, it is not possible, for example, to detect the minimum in the moisture diffusivity in the case of a receding drying front.