An urban forest is of great importance for the urban population. It presents citizens with a place for recreation and relaxation after a busy day. Due to the immediate vicinity of urban life, the introduction of non-native tree species is an especially pressing issue. One of such forests is City forest Celje. It is a forest whit many indigenous and non-native tree species. Without a doubt, the attitudes of individuals towards change can differ greatly, which affects their views towards non-native tree species. For this reason, we conducted research consisting of two major questions: how visitors perceive non-native tree species in the City Forest Celje and how well they know them. The results show us that non-native tree species are recognised well, but opinions differ and there are doubts about the positive effect of non-native species on the environment.