This master’s thesis concerns the performance of professional children’s theatre in public libraries. With qualitative interviews I have looked into how four children’s librarians and two theatre consultants appreciate professional children’s theatre, and furthermore I have looked into their view on the importance of theatre for children. My intentions have also been to investigate their views on the function and status of children’s theatre in public libraries and also the relationship between library and theatre activities for children. The empirical findings have been analyzed using theory and previous research. The quality aspect of children’s theatre has been analysed using Willmar Sauter’s communication model, which analyzes the communication between the stage and the audience. The results show that children’s librarians and theatre consultants believe that the experience of quality is strongly connected to the theatre company’s treatment of the audience prior to the performance and their ability to maintain the communication with the audience through out the performance. The quality of the performance is also influenced by the children’s librarians and the theatre consultant’s perception of the working skills, intentions, conditions of production, and economical conditions of the theatre company. Furthermore the results show that the children’s librarians and theatre consultants are convinced that a positive experience of children’s theatre is potentially beneficial to children, due to its ability to confirm the child’s inner and outer world, and work as a means for processing and reflection. The results show that children’s theatre performed in libraries can serve a useful purpose in the relation between a child and its parents. The children’s librarians all consider children’s theatre to be an integral part of children’s libraries activities.