Although different genome editing tools have been around for decades, the recent emergence of cheap, quick, and accessible CRISPR/Cas9 technology has led to a revolution in this field. The technique has the potential to transform medicine from curative into preventive using a gene therapy. An application of genome editing has proven to be effective for both genetic and non-genetic (e.g. infectious) diseases. However, cancer and rare diseases treatment is at the forefront of interest. Concurrently, the legal and ethical frameworks should be discussed, especially as the technology moves towards a modification of the germ cells or embryos. In addition to a precise molecular genetic diagnosis and choosing the best gene therapy approach for a particular individual, an attention should also be paid to the impacts on the entire human population and the next generations. In this review, we summarize the most important applications of CRISPR/Cas9 technology in the field of medicine. Some interesting results from recent years are presented in the context of used approaches and importance for the future developments in medicine. Finally, ethical and legal conditions in relation to different gene editing applications are discussed.