Clinical issue <p>Monofocal and multifocal bone lesions in children and adolescents may result from various diseases. Apart from inflammatory entities malignancy is the most important issue to be ruled out.</p> Standard treatment <p>Various diseases. Apart from inflammatory origin malignancy is the most important issue to be ruled out. Imaging in particular magnetic resonance imaging (MRI) has an important role for the diagnostic process.</p> Diagnostic work-up <p>Osteomyelitis and septic arthritis on the one hand and nonbacterial osteomyelitis and synovitis, acne, pustulosis, hyperostosis, and osteitis syndrome (SAPHO) syndrome on the other may present with unspecific clinical symptoms and overlapping disease courses.</p> Achievements <p>Radiology is important not only for diagnostics but for treatment planning.</p> Practical recommendations <p>This review focusses on questions to the radiologist from the clinician’s view.</p>