Detailed analyses of speleothems collected in caves of the Demänová Valley, Nízke Tatry, Slovakia, have found significant variability in uranium concentrations and initial ²³⁴U/²³⁸U activity ratios, plus correlation between these variables. They are related to the ages of samples and their differing locations in the caves. Strong variability of initial ²³⁴U/²³⁸U activity ratios is the reason for serious limitations in applying the ²³⁴U/²³⁸U Regional Uranium Best Estimate method as an age estimator for speleothems older than the range of the ²³⁰Th/²³⁴U method (500 ka). The strong variability of uranium contents in speleothems, rocks and waters and their isotopic compositions allowed us to distinguish distinct periods with changes in water circulation paths or distribution/weathering degrees of deposits in surface alimentation areas or in the epikarst zone, that result from the more ready leaching of the ²³⁴U isotope from sediments. Periods characterised with higher initial ²³⁴U/²³⁸U activity ratios are most likely associated with the deposition of “fresh” colluvial deposits and/or soil development (potential uranium source) in the alimentation area. Gradual decrease of initial ²³⁴U/²³⁸U activity values indicate prolonged stable weathering and uranium leaching conditions. The Demänová results indicate periods of intensive erosion and “fresh” sediment deposition in the alimentation areas at ~120 ka, ~80–70 ka, and during the Holocene.