A neutronic method based on neutron thermalization by hydrogen nuclei is used to measure the moisture content in packages of radioactive waste embedded in hydraulic binders. The two steps of the measurement are (a) acquisition of the neutron characteristics of the embedded waste considered (or of a chemically similar material) and (b) the measurement itself obtained with a neutron moisture meter. The neutron characteristics required are the adsorption and diffusion cross sections ∑a and ∑d for thermal neutrons of the dried material. These two parameters are used to calculate the calibration curve (valid only for the material considered) as follows:N = (α·Ds + β)Hυ + γ·Ds + δ,which allows the counting N of the neutron moisture meter to be converted into free-water content Hv (α, β, γ, and δ are deduced from ∑a and ∑d; Ds is the dry density of the material). The neutron moisture meter (containing a fast neutron source and a thermalized neutron detector) is portable. Measurements are taken at various depths in a core hole made in the package to draw a water profile. The measurements are taken in materials used for waste solidification and in active or inactive packages. The results obtained (free-water content) are in good agreement with those obtained by determining the weight loss at 120°C (the differences between these two measurements are generally ∼10% when the free-water content is ∼20 to 25 %). The water profiles allow one to detect the presence of excessive free water.