A method for separating lymphocytes and/or stem cells from whole blood in an automated blood cell separation device, wherein the automated blood cell separation device is not connected to a patient, comprising the steps of - supplying blood to a tubing set including a plasma/buffy-coat tube and installed on the automated blood cell separation device, using blood samples that were already obtained from a patient, - in a separation chamber of a centrifugation unit separating the red blood cell and plasma fractions, with a buffy-coat fraction including lymphocytes and/or stem cells between the red blood cell and plasma fractions,, wherein the plasma and red blood cell fractions are not reinfused into the patient but are collected in collection containers, - accumulating the buffy-coat between the red blood cell and plasma fractions in the separation chamber; - condensating of the buffy-coat fraction in the separation chamber, - spillover of the buffy-coat to the detector device at front panel of the automated blood cell separation device, wherein in a fluid stream the buffy coat fraction follows the plasma fraction and is followed by the red blood cell fraction; - transferring and collecting the buffy-coat comprising the lymphocytes and/or stem cells into a collection container, wherein for transferring and collecting the buffy-coat comprising the lymphocytes and/or stem cells into a collection container, at least two criteria are applied, wherein - a detector device monitors turbidity and colour of the fluid stream in plasma/buffy-coat tube and the transfer of the buffy-coat comprising the lymphocytes and/or stem cells into the collection container is initiated, when as a first criterion the turbidity of the fluid stream in plasma/buffy-coat tube rises indicating that besides platelets lymphocytes and/or stem cells are contained in the fluid stream, and when an absorption signal representing a colour of the fluid stream in plasma/buffy-coat tube increases indicating the presence of lymphocytes and/or stem cells and at least a reduced platelet count in the fluid stream, and - the transfer of the buffy-coat comprising the lymphocytes and/or stem cells into the collection container is terminated when as a second criterion a predefined threshold of the colour of the fluid stream in plasma/buffy-coat tube is reached, wherein the threshold corresponds to a predefined hematocrit value. - supplying blood to a tubing set including a plasma/buffy-coat tube and installed on the automated blood cell separation device, using blood samples that were already obtained from a patient, - in a separation chamber of a centrifugation unit separating the red blood cell and plasma fractions, with a buffy-coat fraction including lymphocytes and/or stem cells between the red blood cell and plasma fractions,, wherein the plasma and red blood cell fractions are not reinfused into the patient but are collected in collection containers, - accumulating the buffy-coat between the red blood cell and plasma fractions in the separation chamber; - condensating of the buffy-coat fraction in the separation chamber, - spillover of the buffy-coat to the detector device at front panel of the automated blood cell separation device, wherein in a fluid stream the buffy coat fraction follows the plasma fraction and is followed by the red blood cell fraction; - transferring and collecting the buffy-coat comprising the lymphocytes and/or stem cells into a collection container, - a detector device monitors turbidity and colour of the fluid stream in plasma/buffy-coat tube and the transfer of the buffy-coat comprising the lymphocytes and/or stem cells into the collection container is initiated, when as a first criterion the turbidity of the fluid stream in plasma/buffy-coat tube rises indicating that besides platelets lymphocytes and/or stem cells are contained in the fluid stream, and when an absorption signal representing a colour of the fluid stream in plasma/buffy-coat tube increases indicating the presence of lymphocytes and/or stem cells and at least a reduced platelet count in the fluid stream, and - the transfer of the buffy-coat comprising the lymphocytes and/or stem cells into the collection container is terminated when as a second criterion a predefined threshold of the colour of the fluid stream in plasma/buffy-coat tube is reached, wherein the threshold corresponds to a predefined hematocrit value.