The article starts with the traditional notion of the critical period hypothesis (Lennne-berg) showing its limitations as the only explanation of children being better language learners than adults. The latter portions are devoted to the description and interpretation of variety of studies which show different factors responsible for the fact that children are not necessarily superior acquirers to adults. The decisive factors causing the differences between the two groups are: 1. physical, cognitive and psychological differences, 2. different conditions in which they acquire a language, 3. different inputs they are exposed to.