This thesis examined self-concept from both a theoretical and applied perspective. It is written as a series of research papers, each of which investigates a specific aspect of this topic. These papers are preceded in Chapter 1 by a comprehensive review of the most relevant research in this area of empirical investigation. The most significant development in self-concept research over recent years has been the shift from a unidimensional model to a multidimensional model that is hierarchically organised. However, this hierarchical structure has received weak empirical support. The study in Chapter 2 revisited this hierarchical model and found stronger support for it than has been hitherto available from previous studies. The acceptance of a multidimensional model of self-concept has inevitably raised key questions regarding the relationship between global and specific domains. In particular, the question as to whether the contribution of a specific domain to global self-concept may be larger when its perceived importance is greater has been the subject of a number of studies. However, there has been little or no support for the importance hypothesis from many of these studies. In Chapter 3, the importance hypothesis was again tested with alternative regression models. The results of this study provided varying levels of support but did not conclusively disprove the conclusions of previous studies. Despite the absence of conclusive proof, the findings nevertheless challenge recent thinking on the limited role of the importance hypothesis and highlight the possible therapeutic value of addressing the importance of domains as a means of enhancing self-concept. The final study in Chapter 4 was designed to access the personal perspectives of participants with regard to the impact of stressful life experiences on selfconcept. This study also evaluated the effectiveness of a personalised intervention programme to facilitate the enhancement of self-concept in the context of the importance hypothesis, and the results provided contrasting levels of support for its effectiveness. The thesis concludes in Chapter 5 with a review of the theoretical and applied implications of the various studies together with implications for future research