The authors present a very rare case of juvenile spondyloarthritis and chronic recurrent multifocal osteomyelitis overlap syndrome in a 16-year-old girl and discuss diagnostic difficulties associated with this case. Juvenile spondyloarthropathies are a type of rheumatic diseases characterized by non-symmetrical peripheral arthritis and enthesitis as well as by spondylitis. Chronic recurrent multifocal osteomyelitis is a rare, possibly autoimmune disease found primarily in children and adolescents. The disease is characterized by bone marrow inflammation and the presence of lytic and sclerotic lesions. Diagnostic imaging plays a key role in the identification of both diseases. The primary modality is X-ray; however, currently, magnetic resonance imaging and ultrasound are increasingly important. A correct early diagnosis allows one to start appropriate treatment to reduce the consequences of these diseases.