Idiopathic scoliosis is the most common form of spinal deformity in children. However, secondary causes of scoliosis, such as ganglioneuroma, should be always considered to avoid wrong diagnosis, and further investigations are required when there are atypical signs. We report a case of ganglioneuroma misdiagnosed as idiopathic scoliosis and review the literature to identify the red flags useful for physicians during the evaluation of a child with scoliosis. On the basis of both clinical and radiographic criteria that emerged from this study, we propose an algorithm that could help in the differential diagnosis, suggesting when to perform an MRI.