Post-transcriptional modifications of mRNA molecules in viruses belonging to the Poxviridae family, including the vaccinia virus, play a key role in regulating viral gene expression and also influence virus-host cell interactions. These modifications include the synthesis of a 7-methylguanosine cap, 2'-O-methylation, 3' polyadenylation of the mRNA strand, hydrolysis of the 7-methylguanosine cap, and 5' polyadenylation of the mRNA strand. Studying post-transcriptional or co-transcriptional mRNA modifications in Poxviridae viruses can contribute to a better understanding of viral pathogenesis and the development of new strategies for treating infections caused by viruses in this family. The aim of this bachelor's thesis is to summarize current knowledge of co-transcriptional or post-transcriptional mRNA modifications in Poxviridae viruses, with a special focus on vaccinia virus.