This thesis provides an insight on the importance of age in first, as well as second language acquisition. The first chapter deals with first language acquisiton while the second one presents similarities and differences between first and second language acquisition. In the third chapter, the age factor in first language acquisition is being discussed, i.e. the existence of the critical period hypothesis in first language acquisition along with an overview of the most important studies. Furthermore, the relation between the age factor and second language acquisition is being studied. Differences between the critical and sensitive period hypothesis for language acquisition are specified after which the most important studies in that field are presented. There is an emphasis on studies which argue that older learners are better than the younger ones and showed are the results of the artificial language study. The last part of the thesis discusses the optimal age for language acquisition and final remarks are given.