In the recent decades, attempts have been made to create a balance between studies of the negative aspects of human character and the positive aspects of human development, such as life satisfaction and strength of character (
1). Positive psychology is a term for positive emotions, positive character traits, and enabling instruction (
2). Seligman has also developed the concept of learned optimism. He argues that positive thinking, or optimism, results from styles of thinking about causes. These styles are called explanatory styles (
3). According to these explanatory or attributional styles, the way that people explain events may influence aspects of their development and health (
4). A small number of studies have been conducted on the optimistic attributional style. For example, some studies showed that people made more internal attributions for achievement than for failure, but self-esteem moderates this relationship: that is, people with high self-esteem made more external attributions for failure than those with low self-esteem. An increase in motivation can also change this relationship: when high motivation accompanied high self-esteem, people made more external attributions for failure (
5). Positive psychological adjustment is indirectly associated with internal, unstable, and controllable attributions (
6). Positive psychology is a scientific study of the way that positive experiences and individual character can facilitate human development. Its aim is to create a framework for happiness within three dimensions, those being a pleasant, engaged, and meaningful life (
7). On the other hand, a considerable amount of research has examined how having a pessimistic attributional style can influence the symptoms of trauma (
4). A pessimistic attributional style is the belief that a good event is caused by external, unstable, and specific factors and a bad event is caused by internal, stable, and global factors (
8). A number of studies have investigated the relationship between pessimistic attributions and other characteristics. For example, Kamen and Seligman (
8) reported that there is a positive relationship between pessimism and the risk of poor heath, infectious disease, and early mortality. Many studies have shown that pessimism is associated with clinical depression (
2,
4,
9-
14), and it has also been found that internal, stable, and global attributions for a specific negative event are associated with clinical depression only when the event was attributed to uncontrollable causes. Learned helplessness as a model of one type of severe clinical depression is supported in studies by Abramson, et al. (
15). Other results have also shown that a helpless attritional style is correlated with both anxiety and depression in males (
16). In addition to increasing depression, having a pessimistic attritional style predicts a decrease in physical health as well as academic and occupational achievement (
8,
13,
17-
21). It has been reported that subjects with the highest depression scores who had a negative attributional style for hypothetical achievement events judged such events as personally important. When they failed a mid-term exam they judged that failing the exam was of major importance. Gray, et al. (
4) indicated that trauma-specific attributions strongly predict symptoms of posttraumatic stress disorder. In general, it is reported that stable and uncontrollable attributions are indirectly associated with negative psychological adjustment (
6). Depression and depressive disorders are highly prevalent in the youth population, and therefore many treatment interventions have focused on this area (
3,
9,
10,
16,
22), and have revealed that cognitive intervention can improve physical health. In the present study a behavioral and cognitive intervention was conducted to change the attritional styles of delinquent boys by using an Optimism Skills Group Training (OSGT), involving discussion, argument and homework. Therefore, this study examined the effect of the OSGT on the change of attritional style from pessimistic to optimistic in boys of the KJCRC. The research hypothesis was that the OSGT would significantly change delinquent boys’ attritional style from pessimistic to optimistic.