A retrospective observational study. We evaluated the prevalence and clinical characteristics of tandem spinal stenosis (TSS) in patients with cervical myelopathy including ossification of the posterior longitudinal ligament of the cervical spine (C-OPLL). Concurrent cervical and lumbar spinal canal stenosis is generally reported as TSS. Most previous studies have used magnetic resonance imaging to evaluate spinal stenosis in the cervical and lumbar spine. The authors performed a retrospective analysis of the outcomes of 297 myelography and cervical surgeries performed in myelopathic patients. We compared the non-TSS group (n = 125) with the TSS group (n = 172) in terms of multiple clinical parameters. In each group, we compared the cervical non-OPLL cases with the cervical OPLL cases. Moreover, we investigated the ratio and clinical outcomes of additional lumbar surgeries performed for TSS patients. One hundred seventy-two cases (57.9%) were considered TSS. Forty-one patients (13.8%) underwent a lumbar operation during the follow-up period. The TSS group included a greater number of OPLL patients, elderly patients, diabetes mellitus, hypertension, and non-smokers than the non-TSS group. The postoperative C-JOA score and the C-JOA recovery rate in the TSS group were significantly lower than the non-TSS group. In the TSS group, the non-C-OPLL patients were significantly older than the C-OPLL patients. The C-OPLL patients had higher postoperative C-JOA scores than the non-C-OPLL patients in both the TSS and non-TSS groups. The additional lumbar surgery effectively improved both the C-JOA and L-JOA scores in TSS patients. The prognosis for TSS patients with myelopathy was worse than that for patients with isolated cervical lesions. Younger C-OPLL patients, even those with TSS, showed higher recovery rates than non-C-OPLL patients. Aging and coexistent lumbar lesions may influence the recovery process following surgery for cervical myelopathy. 4.