Wider use of alternative energy sources is a real requirement of sustainable economy – not only from the point of view of limited natural resources –, and there is a question what is the knowledge, the attitude of young generation. As there is a strong connection between the use of renewable energy and sustainability, the issues must be examined together. On the other hand it can be observed that there is a tendency that people are becoming more open and inquiring towards renewable energy sources, and environment protection is considered as a very important task. The main goals of the research were to examine the knowledge of the young generation taking part in higher education on sustainability and alternative energy, and to find out their attitudes to the use of different alternative energy sources. Also, our hypotheses said that the level of knowledge of sustainability and their attitudes to the environment issues are connected. We compared the results of two surveys carried out in 2014 among the students of a Hungarian and a Slovak higher educational institute. According to the primary results it can be stated that the increasing environmental awareness of young generation is visible, although as for the concepts of sustainability and their knowledge on alternative energy sources, as well as their expectations for the future, there was no significant correlation between their opinions in the Hungarian sample. It was proved that they have open minds towards environmental consciousness, and follow the renewable energy sources with attention. A bit more than a half of the sample has real knowledge on sustainability – we mean the three-pillars model here –, more the mail interview has higher knowledge and for the future they thought the question as a very important one. Considerable majority of the respondents, compared to their capabilities, try to live environmentally-sound life, will do more than one thing to save their environment, although also some negative responses slightly appeared in the received results. Primary results of the Slovak sample are similar; respondents do similar measures for environment at their households as their Hungarian colleagues, but with different priority. Concerning the knowledge of concept of “green economy”, “blue economy” and the “non-growth”, it can be summarized that the awareness is evident but in many cases, there is just few information and weak knowledge connected with the terminology and practical consequences. We think it is an important task of education to increase the awareness of young people on sustainable energy use and to let them accustomed to the thought of green economy and non-growth theories, since the expansion of knowledge may help in the development of a more positive attitude, which will then, hopefully, encourage their actions in the future.