Narcissists cheat on their spouses, commit adultery and have extramarital affairs and liaisons for a variety of reasons which reflect disparate psychodynamic processes. (From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 2 DVDs with 12 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)