Cesium-137 content in lichens and mosses from northern Greece was meas
ured for regular periods of time during the 5 years following the Cher
nobyl reactor accident. A clear increase of the cesium interception wa
s observed for about 2 years after the accident. Later a gradual decre
ase was detected that depended on the habitat and the collected specie
s. A great variation in values was observed when comparing contaminati
on in all the habitats investigated during the same collecting season.