This thesis aims at studying personal pronouns from two perspectives: Systemic Functional Linguistics (SFL henceforth) and Cognitive Linguistics. The experiential metafunction of SFL is used to determine if different speakers assign different participant roles to personal pronouns to serve their different ends. The interpersonal metafunction of SFL is used to check if the use of personal pronouns can reflect the social status of speakers and detect whether they are credible in their speech. As far as Cognitive Linguistics is concerned, this thesis attempts to apply cognitive models like the Attention Model (Langacker, 1987 & 2008) and the Force Dynamics Model (Talmy, 2000) to see if personal pronouns can be used as a tool of exertion of power in discourse. The corpus of this study belongs to a discourse that is an ‘exercise of power and of power over meaning’ (Goodrich, 1987: 2): the legal discourse. This corpus pertains to two genres of legal discourse: Life Insurance Contracts and Court Hearing Transcripts. These genres are chosen because one of the important goals of this thesis is to discover whether the variable of genre affects the distribution of personal pronouns and their participant roles in legal discourse. In order to achieve the aforementioned aims, a variety of quantitative and qualitative tools are employed in the methodology of this thesis. The UAM CorpusTool is used to annotate all the instances of personal pronouns according to their context in the corpus, the participant roles assigned to them and their sources. After annotation, the statistical tools of frequency distribution and the Chi-square test are used to test the hypotheses of this thesis. On the qualitative paradigm, an in-depth study of the use of some personal pronouns using the SFL and Cognitive Linguistics approaches for interpretation is carried out. It has been concluded that the choice of certain personal pronouns and of certain participant roles assigned to them is genre specific. Indeed, the genre of the corpus dictates certain preferences of reference density and of processes and participant roles. These preferences are also dependent on the aims of each genre. It has also been found out that the power dynamics holding between the different participants of each genre and between the different types of participants in court hearings affect the choice of personal pronouns and the participant roles assigned to them. The results have led to the conclusion that this choice is also influenced by the different objectives these different participants seek to achieve in different legal settings.