In the area of the Dyje-Morava floodplain, multiple changes occurred in the hydrological regime due to river regulation. The aim of the study was to find the growth response of pedunculate oak and narrow-leaved ash to changes in the hydrological regime of particular sites. Within similar site conditions expressed by the Querci robaris-fraxineta gcobiocoene type, 4 plots were distinguished with oak and ash stands of about the same age (100-120 years). Each of the plots is characterized by the different combination of changes in the water regime. In each of the plots, increment cores were taken from 16 oak and 12 ash trees, radial width of annual rings was measured and annual ring areas were calculated. Results were correlated with the course of weather in particular years and changes in the water regime or with the occurrence of floods and changes in groundwatcr table. The diameter growth in tree species is an unspecific reaction which is influenced by a great number of factors. In addition to the water regime changes it is also the weather which certainly has an important effect in individual years (precipitation, summer temperatures, incidence of frosts, etc.) and combines with the effect of management measures (both oak and ash are light-requiring species and exhibit a strong response to thinning) and sometimes also with defoliations. The results of the visual evaluation should therefore be considered preliminary and cannot be generalized. Yet, it appears that some growth responses and trends in oak and ash can be explained exactly by changes in the water regime.