Objective To investigate the surgery tactics for ossification of ligamentum flavum (OLF) associated with dural ossification (DO) in the thoracic spine and the cl inical outcome. Methods Between June 2006 and December 2009, 98 patients with thoracic spinal stenosis secondary to OLF were treated, and DO was found in 18 cases during operation. There were 11 males and 7 females with a mean age of 58 years (range, 46-73 years). The disease duration ranged from 5 to 48 months (mean,20 months). All patients underwent surgical decompression because of recent neurological aggravation. Both DO and OLF were resected with octagonal decompression by dissecting pedicle flavum tunnel. The Japanese Orthopaedic Association (JOA) score, modified Oswestry Disabil ity Index (ODI), and the Cobb angle were used to evaluate the effectiveness. Results The initial symptoms were significantly alleviated postoperatively. All patients had transient cerebrospinal fluid (CSF) leakage postoperatively, the CSF leakage disappeared after 8-10 days of conservative treatment. All the incisions healed by first intention. There was no complication of neurologic function deterioration, meningitis, wound infection, or spinocutaneous fistula. Eighteen patients were followed up 20-60 months (mean, 49 months). No recurrence of spinal cord compression symptoms,or neurologic function deterioration was observed at last follow-up. The JOA scores and effectiveness and modified ODI scores were significantly improved after 1 month and 12 months of operation when compared with preoperative scores (P lt; 0.05). The Cobb angles of kyphosis of the involved vertebrae were (6.7 ± 1.6)° before operation and (8.0 ± 1.2)° after 12 months of operation, showing significant difference (t=4.000，P=0.001). Postoperative T2-weighted axial MRI, sagittal MRI scan, and short T1 inversion recovery MRI showed that compressed deformity of the spinal cord returned to normal. Conclusion The surgery tactics for thoracic spinal stenosis secondary to the OLF with DO is safe, and no patching dura mater tears is effective.