The authors determined the concentration of dissolved organic carbon (DOC) and electrical conductivity, as well as the colour and pH in the ground waters of 26 peat-bogs in Pomerania (NW Poland). Three kinds of peat-bogs have been taken into account - forestless sphagnum-cover bogs, bog coniferous forests and birch swamps. The condition of bogs was classified as good, moderate or poor as regards their natural qualities. In good natural-status peat-bogs the lowest amounts of DOC (about 30 mg C dm^-3) and conductivity (<100[mi]S cm^-1) were found in the water of the peat of sphagnum-cover bogs, higher levels were recorded in forest peat-bog water (DOC - 50 mg C dm^-3, conductivity - 100[mi]S cm^-1). Drainage of all the kinds of peat-bog under study leads to an increase in the concentration of DOC (>70 mg C dm^-3) and conductivity (up to 90 [mi]S cm^-1 in degraded sphagnum-cover bogs and 140-150 [mi]S cm^-1 in degraded forest bogs); there also occurs an increase in acidity (from pH 4.0-3.7 to 3.7-3.4) and coloration (from 300 to 1000 mg Pt dm^-3 in forestless peat-bogs and from 600-800 to 1400-1600 mg Pt dm^-3 in forest bogs).