The objective of the present research is to evaluate the incidence and independent predictors of delirium observed among patients after cardiac surgery. Moreover, to asses the sensitivity and specificity of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria (DSM-IV) and International Statistical Classification of Diseases and Health Related Problems - Tenth Revision criteria (ICD-10), and the cut-off values of the Memorial Delirium Assessment Scale (MDAS) and Delirium Index (DI) in diagnosing postoperative delirium.