Measurements of H2 content in UO2 samples have been carried out on the basis of a technique using a hydrogen sensitive sensor of Pd–SiO2–Si. A specially made set up allowed to register the amount of H2 in UO2 samples up to 10–10, g. Measured H2 content in investigated samples was 8, 32 and 102 ppb (mass) at 400, 800 and 1600°C, respectively.