A large amount of liquid radioactive waste has been generated at the Ignalina Nuclear Power Plant (NPP), Lithuania, during its operation. The contaminated liquids are treated with ion exchange-resins, which will generate significant waste stream for cementation. The cemented waste will be disposed of in a near-surface repository. The preliminary safety assessment uncovered that 14C is the most significant radionuclide affecting long-term safety of the closed repository. The method of combined acid striping and wet oxidation with subsequent catalytic combustion has been applied for 14C measurements in cemented ion-exchange resins. It allows separating organic and inorganic compounds from the same sample. At first, the inorganic fraction was extracted by adding acid to the sample followed by absorption of CO2 in a pair of alkali gas washed traps. The remaining carbon was extracted by application of a strong oxidizer. The preliminary results show that activity concentration of 14C in the solidified waste has an order of magnitude of tens and hundreds Bq per gram.