The field of circulating tumor cells (CTCs) is expanding with the development of new technologies, all offering different approaches for isolation and characterization of CTCs from blood. CTCs are tumor-derived cells present in the peripheral circulation. They are used as multifunctional biomarker for selection of therapy, monitoring and follow up of patients and detection of resistance to therapy. CTCs are very rare cells, so detection requires a sensitive method able to differentiate CTCs from hematopoetic cells. The aim of this master thesis is to provide an overview of current methods for CTC isolation, discuss the advantages and challenges of each technology and present the results of isolation of MDA-MB-231 breast cancer cells from whole blood by using ScreenCell device. CellSearch® system, immunomagnetic technology is the reference method for the CTC isolation and detection. It is the only CTC technology approved by the FDA for monitoring patients with metastatic breast, prostate and colorectal cancer. This method uses specific epithelial biomarkers expressed on the cell surface to capture cells and is therefore suitable for tumors of epithelial origin. New technologies, such as Magsweeper or microfluidic devices, do not require pre-analytical processing of blood samples, but they offer CTC isolation of high specificity and sensitivity. Strategies for CTC isolation based on biophysical properties have gained increasing popularity because they are “label free”. One example is ScreenCell®, a simple and innovative non-invasive technology for isolating CTCs from whole blood based on the microfiltration. It is a simple and inexpensive device that provides fast and efficient isolation, but as size-based technology, have risk of device clogging. A pilot study was conducted to evaluate the ScreenCell® system. The goal is to isolate the MDA-MB-231 breast cancer cells in different concentrations from whole blood. Based on the observations and results, the conclusion is that the key preanalyticals requirements for the successful CTC isolation from whole blood using ScreenCell system are the good quality of the blood sample and the time from sampling to CTC analysis. Improvements in existing technologies and a new innovative approaches are confirming the clinical utility of CTCs and accelerating the implementation of liquid biopsy and CTC analysis in clinical practice in oncology.