Many studies have shown that small climate changes can strongly affect the forest trees growth rate, many times causing changes in species habitats. In general, drought is mentioned as the main problem, so it is necessary to carry out its identification and quantification to investigate its effects on forests in Republic of Srpska. This study aims to analyse the relationship between the growth of European beech (Fagus sylvatica L.) at optimal altitudes in the Republic of Srpska and its climate characteristics represented by the Forestry Aridity Index (FAI) and Ellenberg’s climate quotient (EQ) for 1950-2015 timespan. FAI and EQ were calculated using climate data (temperature and precipitation) extracted from a gridded dataset (E-OBS). Sampling was carried out in two localities near Vlasenica and Mrkonjić Grad at 1050 and 1030 meters above sea level (m a.s.l.), sampling the cores from 15 dominant trees at each locality. Using the Pearson Correlation Analysis, a negative impact on tree rings width (TRW) with rising index values was identified. This is especially pronounced for the index values of the year prior to the ring formation. In general, stronger negative correlations between TRW and EQ are found for the locality near Mrkonjić Grad, while FAI index showed a greater negative impact on TRW for the locality near Vlasenica.