This is a multicenter non-interventional observational study conducted with a single hand arm to collect real-world data. In this study, commercially available acalabrutinib will be used as prescribed treatment for CLL as per the treating physician's best clinical judgement. No additional procedures besides those already used in the routine clinical practice will be applied to the patients. Treatment assignment will be done according to the current practice. A multi-center collaborative effort in 15 centers selected from regions within Russia will help capture more patients into the database, rather than limiting the data to a single institution. This will be critical for: * increasing database sample size * reducing bias (single institution bias) * increasing result's generalizability to the whole Russian population Being an observational study, only data available from routine clinical practice and standard of care (SoC), in line with national and international laws and regulations, will be recorded. Patients will be treated according to prescribing information, with visit frequency and assessments performed according to routine medical practice and SoC. Only data corresponding to these visits and assessments will be collected as part of the study. Data for the study will be transcribed and entered into an electronic Case Report Form (eCRF) from the patient's medical records. The site investigator will be responsible for ensuring that all required data is collected and entered into the eCRF with the involvement of clinical research organization