Various types of abnormal posture are observed in Parkinson's disease (PD). Lateral flexion is very common and frequent among them. The clinical characteristics of lateral flexion in PD vary and are classified into two types, the chronic and subchronic types. The chronic type of lateral flexion in PD appears subclinically and worsens, which is related to the laterality of parkinsonian symptoms and the progression of the disease. The subchronic type of lateral flexion in PD develops subacutely and worsens rapidly in several months. An atypical and rare type of tonic truncal dystonia, Pisa syndrome, may be induced following the intake of neuroleptics. The clinical features of the subchronic type of lateral flexion in PD are similar to those of Pisa syndrome. Differences between lateral flexion in PD and Pisa syndrome are described.