This book explains how forensic psychiatry and canon law understand personality disorders and their influence on matrimonial consent. This study is a response to personality disorder cases in the Catholic Church in general and the Syro-Malabar Church in particular. From the forensic psychiatric perspective, each of the ten personality disorders is studied with a description of its characteristic features and diagnostic criteria from DSM-V-TM and DSM-IV-TR. The study contains a brief analysis of Rotal decisions from 2000 to 2004. Personality disorders are divided into three Clusters. At the end of each Cluster, there is an evaluation of the mental capacity or competency of those affected by such personality disorders from both forensic psychiatric and canonical points of view. Four Rotal decisions on obsess compulsive personality disorder from four languages are explained in some detail to demonstrate the general pattern followed by the judges of this Apostolic Tribunal. For the completion of the statistical analysis, mixed and not otherwise specified personality disorders are also included together with Cluster C. There are also references to Dignitas Connubii and Indian civil law.