Diffusion tensor imaging (DTI) is an advanced MRI technique that measures the microscopic molecular motion of water to gain information about the brain structure. This modality and its application to fiber tractography (FT) can be used to study the neuroanatomical background of brain malformations. This thesis aims to give an overview of the application of DTI and FT on pediatric posterior fossa malformations. In the first part we describe the technical underpinnings of DTI and FT and we discuss the limitation to clinical application. In the second part we present some cases (« The molar tooth »,« the squeezed cerebellum » and « The butterfly ») in order to illustrate the additional information that DTI and fiber tractography are providing compared to conventional MR sequences and we discuss their significance.