Cs-137 is one of the most important radionuclides released in the course of atmospheric nuclear weapon tests and during accidents in nuclear power plants such as that in Chernobyl, Ukraine, or Fukushima, Japan. The aim of this study was to compare Cs-137 and K-40 concentrations in particular species of mushrooms from selected locations in the Bohemian Forest (Czech: umava), Czech Republic, where a considerable contamination from the Chernobyl accident had been measured in 1986. Samples were collected between June and October 2014. Activities of Cs-137 and K-40 per dry mass were measured by means of a semiconductor gamma spectrometer. The Cs-137 values measured range from below detection limit to 4300 +/- 20 Bq kg(-1), in the case of K-40 from 910 +/- 80 to 4300 +/- 230 Bq kg(-1). Differences were found between individual locations, due to uneven precipitation in the course of the movement of the radioactive cloud after the Chernobyl accident. There are, however, also differences between individual species of mushrooms from identical locations, which inter alia result from different characteristics of the soil and depths of mycelia. The values measured are compared with established limits and exposures from other radiation sources present in the environment. In general, it can be stated that the values measured are relatively low and the effects on the health of the population are negligible compared to other sources of ionizing radiation.