Chronic lymphocytic leukemia (CLL) is the most common leukemia in the developed world. It is the disease of the adults, which occurs more often in men. The discovery of new drugs that target tumor cells has greatly changed the approach in the treatment of patients with tumors, as well as those with chronic lymphocytic leukemia. One of these drugs is ibrutinib (Imbruvica), the first irreversible blocker of Bruton's tyrosine kinase (BTK) to be discovered. BTK is a molecule that plays a key role in the signaling pathway of B lymphocytes, the central cells of CLL. In addition to targeted action, which brings with it better endurance therapy with fewer side effects, this type of treatment has other benefits. The drug is taken orally once a day, which greatly facilitates treatment for the patient. All of the above has led to great advances in the treatment of CLL and has enabled the treatment of patients who are not candidates for chemotherapy or do not tolerate it. This thesis will present the experience of the Department of Hematology of the Clinical Hospital Merkur in the treatment of patients with CLL with ibrutinib. In retrospect, data from 58 patients form BIS were collected and further processed. Of these 58 patients, 41 continue therapy. Of the other 17, six died and 11 stopped receiving therapy. Of these, nine due to progression and two due to side effects. Our results showed a 67% probability of survival after 30 months of follow-up. The obtained results showed that ibrutinib is an effective and safe therapy in a certain indication.