Focus of this thesis is to compare legislation of electronic signature in the Czech Republic and in the USA. In first chapter are explained basic terms, such as cryptography, certificate or certification authority. Next two chapters deal with laws concerning electronic communication. In chapter about Czech legislation they are electronic signature law and electronic transactions and authorized document conversion law. Moreover, Czech Republic has to abide EU directive. Chapter about USA legislation consists of ESIGN act and UETA. Following chapter is dedicated to problems caused by imperfect legislation. Last chapter contains evaluation of described legislation.