The considerable impact of beavers on the species' composition and structure of plant communities has led to intensive research on their feeding habits. To date, most of the available data originate from monitoring gnawing on woody plants but they rarely include feeding on non-woody plants. This study presents data on the dietary composition of beavers during the vegetation season based on macro- and micro-histological analysis of 97 faeces. The study was carried out during 2004–2008 at four sites in the Czech Republic. The proportion of particular food components in the macro- and micro-fractions was not significantly different, except for grasses, which were present at higher amounts in the macro-fraction. There were no differences in the dietary composition between sexes or between age groups. Generally, beavers consumed mostly deciduous trees and forbs. Consumption of grasses, aquatic plants and field crops was negligible. The seasonal and spatial variability in the dietary composition were influenced mostly by differences in the amount of deciduous trees and forbs in the diet. In spring, beavers consumed mainly deciduous trees. During summer and autumn, the proportion of forbs significantly increased at all study sites even though they dominated over deciduous trees only in the Bohemian Forest. High intra-specific variation in the amount of deciduous trees and forbs in summer faeces led to testing the influence of habitat structure on the dietary composition. The amount of deciduous trees in faeces positively correlated with the diversity and cover of riparian stands. The results showed a high degree of ecological plasticity in diet selection by reintroduced Eurasian beaver in the Czech Republic, but so far, there is no evidence that they cause high levels of damage to economically important trees or field crops.