To diagnose constipation accurately in self-reported constipated patients is very important not to miss organic disease and prevent therapeutic abuse. To investigate the etiology of functional constipation is also important to determine the therapeutic modality of constipation. In this systemic review, the clinical usefulness of symptom evaluation, diagnostic tests to rule out organic and systemic disease, and functional tests to discriminate underlying pathophysiology in the diagnosis of constipation were discussed. No specific symptoms or tests were available to predict organic versus functional constipation or differentiate slow transit constipation versus evacuation disorder. Therefore, collaborative studies are necessary to determine the pathophysiology of this disorder.