Research using lichens as bioindicators of air pollution has been conducted in the city of Łomża. The presence of indicator species of epiphytic and epilithic lichens has been analysed. A 4-point lichen scale has been developed for the test area, on the basis of which four lichenoindication zones have been determined. The least favourable conditions for lichen growth have been recorded in the city center. Green areas and open spaces are the areas with the most favourable impact of the urban environment on lichen biota.