Irrational beliefs are believed to be the source for many psychological disturbances. For example, rigidity is associated with anxiety problem and worry is associated with depression. This shows that irrational cognitions play a key role in the development and maintenance of emotional disturbances. In some studies women compared to men showed statistically significant higher scores on Worrying, Need for Approval and on the total Irrationality scale, whereas men had a higher score on Rigidity. Such types of studies were not conducted in Ethiopian context This book sees the five types of irrational beliefs (Worrying thoughts, Rigidity, Demand-for- approval, Problem avoidance, and Emotional irresponsibility) with respect to some demographical variable For example this book will; evaluate gender difference in irrational beliefs, analyze questions such as; does education makes people rational?, What about age? .... Hence, this book will assess types, level and associations of irrational beliefs with respect to respondent's demography in some selected Ethiopian population. Furthermore, this book will help as source of information for psychologists, researchers, and even for administrator