We present our work as psychoanalysts in the interdisciplinary psychosomatic unit of a paediatric hospital. As the starting point for our work we use Winnicott’s understanding of the psychosomatic dilemma delineated in his paper on psychosomatic illness in its positive and negative aspects. The central hypothesis is that splitting the medical field into many highly specialised fields can be understood as a display of the psychosomatic patients’ inner need for splitting and their defence against integration. Based on four case examples from different developmental periods, we demonstrate the interconnectedness of the relational environment, developmental processes, and psychic and biological conditions, and show how early experiences of threat and deprivation can cause the soma-psyche unit to fragment. Drawing on several psychoanalytic psychosomatic schools, we delineate treatment principles of the psychoanalytic contribution to the interdisciplinary work and of the individual psychoanalytic treatment.