The research of speech difficulties and factors which influence the development of speech had as a goal to explain the development of speech, the factors that influence its development and speech difficulties of children of pre-school age. In the first paragraph “Introduction” the composition of final paper is explained. In the second paragraph “Speech” the speech is defined, its importance for people, the difference between speech, language and communication and the organs of speech important in development of speech are described. In the third paragraph ”Development of speech” the phases of speech through which children pass during their lifetime are described, The fourth paragraph entitled “Speech difficulties” explains the types of difficulties that can be seen in children of pre-school age which are: sigmatism, rhotacism, lambdacism, kapacism, gammacism, thetacism, deltacism, etacism and tetism. In that paragraph stuttering, hastiness, bradylalia, „chanting speech“ and other causes of speech disorders are described. The fifth paragraph “Factors which influence the development od speech” is divided into two parts: “Inside factors” and “Outside factors” where their influence of speech and its development are described. In the sixth paragraph “Research of speech difficulties in children of pre-school age” the target of research is described, hypothesis, materials and methods, subjects who participated in the research and the process of the research. At the end of the paragraph the results together with graphs and tables are described. “Conclusion” is described in the seventh paragraph. At the end of the paper there are the list of literature, tables, graphs and pictures and attachments used in the research.