This study analyzed the postoperative results of surgical treatment for thoracic and cervicothoracic myelopathy caused by ossification of the posterior longitudinal ligaments (OPLL) or ossification of the yellow ligaments (OYL) in 22 patients using magnetic resonance imaging (MRI), myelography and computed tomography (CT). Anterior procedures were performed in 11 patients for OPLL, while posterior approaches were adopted for the management of 11 patients for both OYL and OPLL combined with OYL lesions. Clinical symptoms were improved using both anterior and posterior techniques. MRI and myelo-CT studies, which show the direction of cord compression, the form and extent of the lesion, and the degree of thoracic kyphosis, are very useful when the surgical procedure for OPLL and OYL in the thoracic and cervico-thoracic spine is selected.