Gene therapy is a technique that adds a new gene or replaces or repairs a mutated (changed) gene within body cells in order to prevent or treat certain diseases. Viral or non-viral vectors are used to facilitate gene transfer into the cell. With the progress of science and the discovery of vectors, gene therapy has gained importance and its application for medical purposes is increasing. The use of gene therapy allows doctors to treat cancer, genetic disorders or infectious diseases by changing a person's genetic structure instead of using drugs or surgery. This technique is not fully developed and problems arise when choosing the ideal vector. It is necessary to find a vector that would participate in the repair of the genetic mutation and thereby accelerate the cure of the disease. Viruses have the ability to infect and transfer their genetic material into a cell. It is precisely because of this ability that they are of great importance in gene therapy. Of the large number of clinical trials conducted, there are very few successful and approved therapies. Gene therapy shows promising results and in the future its use could be more accessible to the entire population.