[en] The globally distributed beta-emitters tritium (³H) and radiocarbon (¹⁴C) in the Ignalina NPP (INPP) region and in the background regions have been studied in precipitation, annually growing terrestrial and aquatic plants, tree radial rings, surface water, in unconfined and, at smaller scale, in confined groundwater. The biota samples for ³H and ¹⁴C measurements were collected in co-operation with Dendrochronology Laboratory of the Vytautas Magnus University. The scintillation forms were prepared using chemical methods: the biota samples for ³H analysis - separating hydrogen from organic matter by oxidation with MnO₂ in high temperature and obtaining chemically bound biota water for measurements of ³H activity; for ¹⁴C determination - by preparation benzene form from organic carbon. Conventional LSC methods have been used for ³H and ¹⁴C determinations. The annual ³H variations in precipitation were studied more in detail in 1997-1998 collecting monthly-integrated samples. The annual average activity of ³H in precipitation of the INPP region in 1997 was 16.6 TU, when in winter season it was 11.7 TU and in summer season - 20.2 TU. The ³H activity in precipitation of the background region in 1993 was the following: annual average - 15.5, in winter season - 11.7 and in summer season - 21.3 TU. The influence of the INPP on the ³H activity in precipitation, according to the data of monthly-integrated samples of precipitation, was not observed. Terrestrial plants assimilate ³H and ¹⁴C: the ³H - in processes of moisture transfer; and ¹⁴C - from atmosphere using CO₂ in processes of photosynthesis by plants. For the evaluation of the ³H and ¹⁴C variations in the atmosphere under the influence of the INPP, the activities of these isotopes in annual rings of pine tree (Pinus sylvestris), annual terrestrial plants (Artemisia L.) and tree leafs (Alnus) were studied. Three pine model trees were selected for background area. The maximum and minimum of ring increment coincide in these models very well up to 1961. The maximum of ³H activity falls to 1963 for the background tree model and makes up 1665 TU (1 TU=118 Bq/m³ of biota water), the maximum of ¹⁴C activity falls to 1964 and makes up 199.2 pmC (1 pmC=2.27 Bq/kg of carbon). The 3H activity in the ring of 1995 makes up 25 TU and within the limit of errors coincides with the ³H activity in precipitation of warm season. In the rings of 1987, 1989, 1991 and 1993 of the pine, which grew near the INPP, the ³H activity somewhat exceeded that caused by global factors. Both, in the case of ³H and ¹⁴C, the maximum of radionuclides, generated by nuclear tests in the atmosphere (1963 and 1964), is observed, however the influence of the Chernobyl NPP remains unrevealed because high activities of above mentioned radionuclides accumulated only near the accident location. The ³H activity in annual terrestrial plants here and there exceeded the level, caused by global factors. Such environs were related to INPP release tracks. The ¹⁴C activity in many studied biotic objects (tree rings, annual plants) did not differ from levels caused by global factors, except those located in direction of the prevailing wind from the INPP. ³H entering the atmosphere from the INPP is observed in biota and exceeds the global level up to 2-3 times in areas located close to the INPP. ¹⁴C releases to the atmosphere from the INPP in the form of CO₂ gives a very inconsiderable increase as compared with the global ¹⁴C level in atmosphere of the region. Peculiarities of ³H and ¹⁴C distribution in aquatic systems are determined mostly by global factors and the rate of water exchange. An extra ³H and ¹⁴C source is peculiar only to cooling basin and other water bodies directly related to INPP. ³H in water of cooling basin has been systematically studied since 1980. The highest activity of this isotope in water of cooling basin (120 TU) was observed in 1988 and 1989. During the last decade the average of ³H activity in water of cooling basin makes up 54 TU, when a maximum of ³H activity in water plants reaches 1245 TU. A background level of ³H in lakes (10-15 TU) was observed in background lake and month precipitation. There was not observed considerably increased ¹⁴C activity either in water, or in water plants, except one case, when the ¹⁴C activity in Myriophyllum spicatum was 133 pmC. It slightly exceeds the level caused by global factors (110-118 pmC)