Hangman's fractures are a rare finding in childhood. In case of suspected or proven child abuse, differentiation with a congenital defect of the posterior arch of C2 is essential. We present the case of a 5-month-old girl, who had a history of being physically abused by one of her caretakers. On the lateral view of the cervical spine, a defect of the posterior elements of C2 and an anterolisthesis of C2 on C3 was seen. CT scan showed a bilateral defect in the posterior elements of C2. No soft-tissue swelling of hematoma was noted. MRI showed a normal signal intensity of the intervertebral disc C2-C3. No haematoma was noted. Clinical examination revealed a slight head lag and local tenderness; there were no neurological deficits. This case shows that the differentiation between a congenital C2 arch defect and a hangman's fracture is precarious. In this case the findings on MRI and CT scan were interpreted as a congenital posterior arch defect (spondylolysis).