A case of a chordoma in the thoracic spine is presented. This is a very rare tumour in this location and should be considered in the differential diagnosis of any posterior mediastinal mass. The appearances on CT and MRI were similar to chordomas described in other locations. On T2-weighted images septae of low signal intensity radiated throughout the large high-signal mass. This feature may be of use in differentiating chordomas from other posterior mediastinal masses.