Objective: Arrested pneumatization of the sphenoid sinus is a developmental anatomic variation but may be confused with serious diseases of the skull base. The purpose of this study was to investigate the prevalence of arrested pneumatization of the sphenoid sinus in paediatric patients with haemotologic diseases like sickle cell anaemia, thalassemia and leukemia. Materials and Methods: One hundred and eight paediatric patients (43 girls, 65 boys; age range: 4-18 years; median age: 13 years) with haemotologic diseases who underwent at least one magnetic resonance imaging of the head and neck between 2010 and 2017 in a single institution were included. Magnetic resonance imaging studies were retrospectively reviewed. Well-defined and fat-containing non-expansile lesions located at the sphenoid sinus region were diagnosed as arrested pneumatization of the sphenoid sinus. Medical diagnoses, lesion sizes, age and sex of the patients were recorded. Results: Five (4.6%) of 108 patients demonstrated arrested pneumatization of the sphenoid sinus (3 girls, 2 boys; age range: 9-18 years; median age: 14 years). One (1.2%) of 83 patients with acute leukemia, 2 (15%) of 13 patients with sickle cell anaemia and 2 of 12 (17%) patients with thalassemia demonstrated arrested pneumatization of the sphenoid sinus. No statistical correlation was found between arrested pneumatization of the sphenoid sinus and possible risk factors like patient age and sex. Conclusions: Patients with haemoglobinopathies like sickle cell anaemia and thalassemia involving red-blood-cells had higher prevalence of arrested pneumatization of the sphenoid sinus than patients with leukemia which involves the white-blood-cells. This supported the suggestion that regional blood-flow disorders induce arrested pneumatization of the sphenoid sinus. Correct diagnosis prevents invasive procedures like biopsy and surgery.