The cranio-atlanto-axial junction (C0-C2) is anatomically and biomechanically the most complex spinal region. It is frequently engaged by different pathologies of tumoral, traumatical or inflammatory origin, leading to spinal instability. The advanced knowledge about the anatomical details, the physiology, the mechanism of injury, the nature of the processes and their classification are crucial for the adequate therapeutic approach when dealing with pathologies in this region. In the actual study we are reviewing the anatomical landmarks, the classification of the pathological processes and the diagnostic options and criterion when dealing with pathologies involving the cranio-cervical region. We are presenting our experience with the posterior screw fixation for the treatment of the craniocervical junction instabilities.