The aim of the study was to evaluate the effectiveness of different imaging techniques with respect to diagnosis and differential diagnosis between Erdheim-Chester disease (ECD) and multifocal fibrosis (MF)/Ormond's disease (OD). Three cases of ECD were included, two of which were misdiagnosed as MF/OD. Findings in different imaging techniques [plain radiography, skeletal scintigraphy, computed tomography (CT) and magnetic resonance imaging (MRI)] of the lower extremities, chest MRI, craniofacial MRI, abdominal CT and MRI) were compared and ranked with regard to diagnostic efficacy. Differentiation between ECD and MF/OD is only possible by imaging the long bones. Bone roentgenograms and skeletal scintigraphy, followed by MRI and CT of the lower extremities are the most effective imaging techniques. A low threshold for carrying out plain radiography of the lower limbs in case of RF/MF will increase the number of ECD-cases.