Posterior interspinous dynamic stabilization is used increasingly in the treatment of lumbar degenerative spinal conditions, with preliminary evidence for its clinical and biomechanical efficacy emerging. The need remains to define patients who respond best to this form of surgery. This study examined clinical outcomes in 39 patients (21 females) with defined lumbar spinal pathologies, for two years after lumbar surgery augmented with the Device for Intervertebral Assisted Motion (DIAM). Anatomical patient categorization revealed involvement of disc (n=25/39) and facet (n=14/39) lumbar pathology, with clinical indications for surgery being: segmental instability (n=21/39); nerve root compression (n=11/39); and facet joint pain syndrome (n=7/39). Pain, function and satisfaction data were derived from MODEMS self-report questionnaires, which were collected prospectively over a two-year post-operative period. Results showed that L4-5 and L5-S1 were the most common DIAM-implanted spinal levels. Clinically significant post-operative improvement in pain (23.4%) and function (13.5%) occurred between three and twenty-four months. Eleven (of 39) required further lumbar surgery. Nineteen (of 28) were more satisfied at 24 months post-operatively compared to baseline. Disc involvement and segmental instability were the most common presenting lumbar segmental pathologies, yet the least successful in response to surgery augmented with DIAM. Patients with facet involvement reported superior improvement post-operatively compared with those with disc involvement. Patients with facet joint disease demonstrate better outcomes at 24 months following lumbar surgery augmented with DIAM posterior interspinous dynamic stabilization, compared with those presenting with disc pathology.