This paper presents a short overview about the discussion about the hydrogeological problems connected with oil shale exploration in NE Estonia. On the basis of the results of the solution to the hydrogeological model developed at Geological Survey of Estonia it was found that the proportion of unconfined groundwater in different open-cast mine fields accounts for 6-34% and precipitation water makes up 66-84% in the depleted area. Presently a unified groundwater model of Estonian-Russian border region comprising a 200x200-km area north from Lake Peipsi is being compiled under the initiative of French Geological Survey (BRGM).