This is a retrospective study of 76 children who had had malignant tumours treated with laminectomy or laminoplasty and/or radiation therapy affecting the spine. Spinal tumours in children are extremely rare. However, their treatment can result in progressive spinal deformity. Radiation therapy affecting the growing spine can lead to asymmetric vertebral growth, causing kyphosis and/or scoliosis. These spinal deformities pose one of the most challenging problems for the spine surgeon. The aim of this article is to describe late-onset post-laminectomy/post-radiation spinal deformities and to evaluate the results of their treatment. Seventy-six children, with a mean age of 4 years and 7 months (range, 2 months to 16 years), underwent surgical removal of malignant tumours, between 1961 and 1995. Sixty-seven of them developed post-laminectomy/post-radiation spinal deformity. Conservative treatment consisted of bracing and corrective plaster casts. In 46 cases the deformity was treated surgically. A distraction plaster cast was used as preoperative preparation in the more severe and rigid curves, with or without neurological impairment. Surgery consisted of combined anterior and posterior fusion in 39 cases and posterior fusion in seven cases. Posterior instrumentation was used in 38 cases. The mean follow-up period was 6 years and 7 months (range, 9 months to 20 years and 2 months). Nine children did not develop deformity following the primary tumour treatment. One of them underwent laminectomy with posterolateral fusion and eight had laminoplasty combined with external immobilisation. Forty-six children developed iatrogenic kyphosis and underwent surgical correction from a mean of 75° pre-correction to a mean of 32°. The mean scoliotic angle correction was 66° preoperatively to 34° postoperatively. At follow-up, the mean correction loss was 7° in the sagittal plane and 5° in the coronal plane. Preoperative distraction plaster cast treatment resulted in a correction of 39% in kyphosis and of 58% in scoliosis, and in a partial or complete recovery of neurological deficits in all but one patient. In severe and rigid curves that develop following treatment of paediatric spinal tumours, preoperative application of a distraction plaster cast can reduce deformity and facilitate surgical correction. Furthermore, in the case of pure bony compression of the spinal cord due to the apical vertebra of the deformity, treatment with the distraction plaster can result in recovery from the neurological impairment. The prevention of post-laminectomy/post-radiation spine deformities is emphasised. Rigid external immobilisation for a period of 4 months in the cervical spine and of 6 months in the thoracic spine is recommended after both laminoplasty and laminectomy with posterolateral fusion.