In this paper, we will make an overview of the relationship between distinct text-forms of the so-called Old Testament, the Septuagint and the Masoretic Text. In that context, we will deal with both philological and theological issues concerning the Septuagint. With regard to the textual differences between the respective text variants, they could be the result of the transmission process and translation process. In the first part of the paper, we will examine possible reasons for textual differences based on transmission process: different textual strands and other internal or external reasons. The second part of the paper will focus on differences which are the result of the translation process and their underlying causes, such as the difference in language systems, the involvement of different translators in the translation process and the context of the translation process. In the third part of the paper, we will deal with the differences created by a different understanding of theological notions in the Septuagint and in the Masoretic Text.