47 lichen species of 21 genera and 7 families are determined in the town of Gomel. Some features of their distribution in Gomel were studied. No correlation has been found between the number of lichen species on a tree and its trunk diameter. Different tree species were found to have different sets of lichen species. Bark pH values were defined for 11 tree species in Gomel. Three groups of tree species have been distinguished by bark pH. The first group includes Acer negundo with the bark pH = 7.17, Populus balsamifera — 6.66, and P. nigra — 6.63; the second one: Acer platanoides — pH = 6.12, Fraxinus excelsior — 5.77, Tilia cordata — 5.53; the third: Aesculus hippocastanum — pH = 4.95, Betula pubescens — 4.89, B. pendula — 4.88, Quercus robur — 4.79, Acer saccharinum — 4.74. Certain species of lichens are confined to these groups: Physconia sp. colonizes trees of the first group (pH 6.0-8.0); Hypogymnia physodes, Evernia prunastri, Melanohalea exasperatula grow on trees of the third group (pH 4.0-5.5); trees of the second group (pH 4.5-6.5) provide a suitable substrate for the most lichen species. Keywords: Gomel, lichens, substratum, bark, acidity, ecology, monitoring.