The thesis is organized as follows. Chapter 2 discusses the notion of information structure.After introducing and defining information structure and its three main parts (topic, background, focus) a brief description of its acquisition is provided. Chapter 3firstly, deals with English word order and scrambling.Secondly, it goes on to explain the nature of English focus and focus particles with reference to their acquisition as well. Additionally, in favour of the better understanding of the latter chapters a relatively short comparison of word order and scrambling in English and Japanese is presented. Chapter 4 is dedicated to the Japanese language; the first part of the chapter describes the characteristics of Japanese word order, scrambling and focus while the second part presents the most significant findings in connection with the acquisition of them. Finally, Chapter 5 describes generallythe experimental methods used to investigate child language acquisition and particularly some concrete examples of experiments that studied the acquisition of Japanese word order, scrambling and focus.