Different calculation methods are applied to determine the natural or specific groundwater vulnerability. Examples are taken from the Hydrogeological Map of Poland 1:50000 and Major Groundwater Reservoirs projects run by the Polish Geological Institute – National Research Institute. For productive aquifers the groundwater vulnerability was assessed in terms of the groundwater hazards. Another approach for the groundwater vulnerability assessment of the top aquifer (first aquifer) is applied where the resistance to the surface pollution is assessed. As far as the Major Groundwater Reservoirs are concerned the groundwater vulnerability is assessed in terms of the travel times of the hypothetical pollution particles. The outcomes of the groundwater vulnerability calculations made for these projects are presented using the example of a typical river valley hydrogeological system – the Pliszka river within the Major Groundwater Reservoir No. 148. A comparison of the results of the calculation methods shows the dependence of these results on the type of the hydrogeological input data.