The current thesis has been prepared in journal format and it reports a systematic literature review, an empirical research study, and a paper on relevant critical reflections. Based on a hybrid cognitive and metacognitive model for social anxiety disorder and on a metacognitive approach to emotional difficulties, the main aim of the thesis was to investigate the potential contributions of metacognitive beliefs to social anxiety over and above that of cognitive beliefs. To this effect, the systematic literature review investigated the nature and strength of the associations between social anxiety and two types of beliefs: cognitive beliefs, referred to as social beliefs, (i.e., conditional and unconditional self-beliefs, and high standards) and metacognitive beliefs (i.e., beliefs about thoughts and thinking processes). Cross-sectional, longitudinal and experimental studies were included, and correlation and regression coefficients, as well as results from group comparisons were extracted. Twenty three papers were reviewed using narrative synthesis. The results showed a robust positive association between social beliefs and social anxiety and suggested a possible mediation effect of cognitive processes. Metacognitive beliefs were also positively associated with social anxiety both directly and indirectly, through cognitive processes. The empirical study expanded on these results by investigating the potential prospective associations between metacognitive beliefs and social anxiety. A sample of 156 university students and staff completed a battery of questionnaires twice, two months apart. Regression analyses showed that irrespective of social beliefs, metacognitive beliefs about the uncontrollability and dangerousness of thoughts were individual positive predictors of and explained additional variance in social anxiety two months later. This effect was partly mediated by self-focused attention. Social beliefs did not show a prospective individual contribution to social anxiety. Following the above, the critical reflections paper focused on the process of conducting these studies. The adopted epistemological stance is discussed and the process of decision making during the various stages of research is expounded. The strengths and limitations, the findings in the context of wider research, and the implications for clinical practice and future research are discussed.