A 38-year-old man with Von Willebrand's disease type 2 came to us for treatment advice in relation to a trip abroad, and also a 53-year-old woman with bleeding treated as idiopathic thrombocytopenic purpura (ITP). In the man, a trial dose of desmopressin led to severe thrombopenia, and in the woman, treatments, such as splenectomy and prednisone in the past, had been ineffective. In both patients further investigations led to the diagnosis 'Von Willebrand-disease type 2B'. Despite the fact that Von Willebrand's disease type 2B has distinctive laboratory characteristics, such as thrombocytopenia, a positive Ristocetin Induced Platelet Agglutination (RIPA) test at a low ristocetin concentration, and an abnormal multimer pattern, some cases have incomplete or atypical presentations which can be misleading for the diagnosis. A wrong diagnosis can lead to ineffective and potentially dangerous therapeutic interventions. Molecular genetic analysis of type 2B mutations is simple and can help in making the correct diagnosis in cases of familial thrombocytopenia or for a further characterisation of Von Willebrand type 2.