The article is devoted to assessing the radiation quality formation of groundwater with anomalous excesses of 234U on example the Pre-Volga region (European part of Russia). It was found that exceeding the reference values of groundwater radiological toxicity in a number of cases is associated with anomalously high activity of 234U. Isotopic (2H, 18O) and chemical data indicate that the anomalous 234U/238U ratios are of cryogenic origin related to the effects of past climatic fluctuations on the aquifers. Such groundwater formed from thawed permafrost at extremely low uranium concentrations may have unsatisfactory radiological quality due to anomalous excesses of 234U.