The aim of this study was to determine the clinical validity of functional flexion/extension radiographs of the cervical spine in a defined patient population. Sixty-four adults with functional disorders of the cervical spine underwent passive flexion/extension radiographic examinations. The radiographs were analyzed using a computer assisted method to calculate segmental motion parameters, such as rotations, translations, and centers of rotation. The patients were separated into three groups based on their specific functional disorders, and their motion parameters were compared with those of a healthy population. The three groups consisted of patients with degenerative changes, those with radicular syndrome, and those with whiplash trauma. Most of the patients displayed trends toward hypomobile segmental motion. This trend is displayed more substantially in the groups with degeneration and radicular syndrome. Hypomobility in segmental rotation was significant at C6-C7 for the degenerative and radicular groups. The trauma group showed trends toward hypermobility in the upper and middle cervical levels, and the locations of the centers of rotation were shifted in the anterior direction when compared with those of the healthy population.