Malformations of the cranio-cervical junction represent a complex entity, comprising neuro-meningeal and bone anomalies. Malformations of the central nervous system are nowadays easily explored using magnetic resonance imaging (MRI), while osseous malformations are classically assessed with standard radiographic techniques, which can give only incomplete information, and are often difficult to realize and analyse. We report a retrospective study of 10 patients with a Chiari malformation operated on in our department at La Salpêtrière hospital, between July 1995 and December 1996 (1 man, 9 women; mean of age: 35 years; postoperative median follow-up: 6 months; 70% of improvement and 20% of stabilisation), and we underline the interest of the systematic pre-operative realization of a 3D CT and angio-CT studies of the cranio-cervical junction. This examination offers advantages of: a precise analysis of the more complex osseous malformations; a study of the relationships between vascular and bony structures; a study of the relationships between neuraxis and spinal and cranial structures; and an optimal planning of the surgical procedure, adapted to the anatomical particularities of the patient.