The non-native tree species were first introduced into the European forests approximately 250 years ago. In the era of a fast technological progress and industrial development, the need for raw materials was growing rapidly. The forestry and wood industry both wanted to keep up, and that is why the non-native fast-growing tree species were introduced. Between 1880 and 1890, this tendency was just as present in the Slovenian forestry, too. The records of that period affirm the introduction of the first non-native tree species in these forests. In the beginning, the new locations were expanding rapidly, but the process later decelerated due to various wars. After WWII, both the mentality, as well as the forest development guidelines, changed drastically. The non-native tree species introduced at the time are more or less still present. Many species quickly became established in their new environment, some are even reproducing and building new stands, while others deteriorated soon after their introduction. Regardless of all good intention, some species have started growing far too excessively. For the next 70 years or so, there was little debate over the non-native tree species; however, they became food for thought once more, mostly because of the immense invasion of numerous non-native plants. Another crucial issue is climate change, because nobody can tell what its consequences are going to be and whether the native tree species will be able to adapt to the new climate conditions in time. And these are precisely the issues that have brought up the question of how to make the onceadded and later almost forgotten non-native tree species useful once again.