The project is being implemented in order to improve the quality and accessibility of healthcare services for children with rare diseases both in the public institution at Vilnius University Hospital in Santaros Clinics and throughout Lithuania. During the implementation of the project, modern medical equipment and furniture, information technology equipment will be purchased, a registration sub-system for patients with rare diseases (children) has been developed and implemented, methodologies for the diagnosis, treatment and/or monitoring of children’s rare diseases have been developed for professionals providing healthcare at all levels for children. This will increase the effectiveness of diagnosis, treatment and prevention of rare diseases in children. The project is expected to increase the number of diagnosed rare diseases in children, improve the effectiveness of treatment and reduce the likelihood of complications. In addition, the acquisition of a system of high performance liquid chromatography with mass spectrometry is expected to extend the range of laboratory diagnostics and monitoring of symptomatic rare children’s diseases, and to introduce extensive laboratory tests. Children (from birth to 18 years old) who will apply to a public institution Vilnius University Hospital Santara Clinics for the diagnosis, treatment and/or monitoring of rare diseases, their parents or guardians, as well as doctors and nursing specialists will benefit from the project.