Therapy planning is a very complex task, being the patient’s therapeutic response affected by several sources of uncertainty. Further-more, the modelling of a patient’s evolution is frequently hampered by the incompleteness of the medical knowledge; it is hence often not possible to derive a mathematical model that is able to take into account the characteristics of the uncertain environment. An interesting way of coping with this class of problems is the Decision-Theoretic Planning approach, i.e. the formulations of policies on the basis of Decision Theory. This approach is able to provide plans in the presence of partial and qualitative information, while preserving a sound mathematical foundation. In this paper we will exploit a novel graphical formalism for representing Decision-Theoretic Planning problems, called Influence View. This method will be tested in an important therapy planning problem: the assessment of the Graft Versus Host Disease prophylaxis after Bone Marrow Transplantation in leukemic children.