The Finnish Gulf is the most vulnerable part of the Baltic Sea. The main reasons for Baltic Sea contamination are direct wastewater discharge, river and underground runoff and oil spills. This article deals with the problem of groundwater pollution in the territory of St. Petersburg. Groundwater from this area discharges directly to the Finish Gulf or into rivers and channels of the gulf. The main goal of this article was to study spatial-temporal changes in petroleum products and heavy metals concentrations in groundwater of diff erent hydrogeological levels. To achieve this goal, data from 150 groundwater wells were analyzed. As result, the most aff ected areas of St. Petersburg and possible polluters were indentified. Refs 7. Figs 6. Table 1.