The present thesis is about how preschool children develop their language skills. The purpose is also to discuss how library and preschool can collaborate and in different ways together help the children to achieve different skills and to use their first and second language in a more appropriate way. The main problem identified from literature and own observations is why library and preschool dont collaborate to help young children to develop their language skills? Which reasons are behind a lacking collaboration? What can be done to increase collaboration between the library and the preschool? How can librarians and preschool teachers use their different professional skills in the best manner to be able to help the children to develop their skills in language acquisition? Is it possible to measure childrens language skills and how can one decide what characterizes a good collaboration? We started with a literature review and continued with collecting qualitative data by means of interviews with people who worked as librarians and preschool teachers, who were supposed to collaborate in a language oriented project. We have chosen different language theories by well-known scientists and we have only picked a few of them, which we considered relevant for the chosen topic. Preschool children are very sensitive to language training, and could benefit a lot by means of professional guidance by librarians and preschool teachers in collaboration. By means of collaboration an increasing demand of services provided by libraries could be predicted. Both short term and long term effect could be predicted. Enhanced language skills could be beneficial for future success in school and working life. However, in the small empirical part of our study the results were discouraging with respect to collaboration. It seems that a mutual collaboration between library and preschool is rare rather than commonplace.