In patients with haematological diseases regular blood count analyses are necessary. In haematology, capillary blood count analyses became established in routine diagnostics. The method and procedure of capillary blood sampling is well accepted by both the patients and the medical personal for a long time. However, only venous values are generally accepted in clinical routine. It is important to know whether or how capillary blood gives discrepant results for the various parameters. Values for therapeutic decisions, e.g. transfusion, are only known for venous values. So far, there are only deficient data available. Therefore, the aim of this study is (i) to compare capillary blood count parameters with the corresponding venous samples to verify the hypothesis that capillary and venous blood count parameters are equivalent, (ii) to include an adequate large number of adult haematological patients (with low and high values) and healthy adults, (iii) to obtain difference values for conversation of measured capillary values into the corresponding venous values.