Lateral bending radiographs are commonly used in surgical planning to assess the flexibility of the spine and to establish the placement of instrumentation. The objective of this study was to determine the relationship between axial rotation and lateral bending in patients with AIS, and to assess the flexibility of the spine in the axial plane. Rotational data were collected retrospectively from 14 subjects (1M, 13F) immediately prior to spinal surgery (age at surgery: 15.0 +/-3.5 years). All subjects had AIS, right thoracic major curves. Rotation was measured from T4 to L4 at every level on the left and right supine bending and standing PA radiographs. The apices of the major and minor curves, the neutral vertebra, as well as the Cobb angles were recorded. The deformity in the frontal plane is flexible and responds to lateral bending. No significant differences in vertebral rotation were found at the thoracic apex or the neutral vertebra in response to lateral bending. Significant differences (p<0.05) were found between PA vs. left bend, and left bend vs. right bend at the lumbar apex only. Lateral bending does not improve vertebral rotation in the thoracic spine, but does so in the lumbar spine. The axial flexibility at the lumbar apex may be attributed to the lack of costal attachments in this region, and the compensatory nature of the lumbar curve. The lack of axial flexibility in the thoracic region may hamper surgical attempts to correct vertebral rotation and the rib hump.