About 21 years after the Chernobyl accident, (137)Cs and (40)K activity concentration measurements using gamma-ray spectroscopy and elemental analysis using energy dispersive X-ray spectroscopy were performed in five different lichen species collected from the Giresun province of northeastern Turkey. Being a symbiosis of algae and fungi, lichens are mostly used for environmental measurements since the fungal partner is responsible for the uptake of necessary nutrients or harmful substances, such as heavy metals of radionuclides. The gamma activity results showed that (137)Cs, an artificial radionuclide released from the Chernobyl power plant accident, is still eminent in the environment of the province. The mean activity concentrations of (137)Cs and (40)K ranged from 24 to 254 with the mean value of 102 Bq kg(-1) and from 345 to 2103 with the mean value of 1143 Bq kg(-1) in dry weight. The results of the elemental analyses showed potassium, calcium, titanium, iron, tin, and barium in different concentrations.