This book represtents a work which evaluates the treatment effects and implementation of Parent Management Training - the Oregon model (PMTO™) to treat children´s behavior problems in Iceland. The intervention is an Empirically Supported Treatment (EST), and originally developed by Gerald Patterson and his colleagues in the United States. Its main goal is to improve parents´ child-rearing methods by breaking coercive patterns between parents and children. The book is built on four papers. The first two papers explored the influences of the implementation and the second two papers evaluated the effects of PMTO in a randomized controlled trial (RCT) in community settings nationwide in Iceland. The main findings of the book are that PMTO led to greater reductions in child adjustment problems relative to the comparison group, which indicates that PMTO is an effective method to treat children´s behavior problems in Iceland and supply evidence for the method´s successful implementation in community settings in the country. Findings also indicate a further need to adapt observational measures to Icelandic cultures.