Lately we often hear allegations that a certain work is a plagiarism, hence I decided to describe this area in detail in my diploma thesis. First I define what precisely the term plagiarism means, in which areas it is present, how to limit it, and how to utilize software for its detection. I delve into the utility of software which detects details in source code and text documents. Such software does not determine plagiarism itself, but rather indicates the percentage of text or source code similarity, which we can subsequently treat as plagiarism. Original works are individual intellectual creations from the fields of literature, science, and art expressed in any form. Authors’ rights are divided into economic rights, moral rights, and other rights. Plagiarism therefore constitutes a violation of authors’ rights. It is however, at present exceedingly difficult to ascertain whether a work is a plagiarism or not, since we normally have a very limited number of databases at our disposal.