Introduction: Simple bone cyst is benign fluid-filled lesion localized mainly in long bones. It is usually diagnosed in the first two decades, the most common in proximal humerus. Unicameral bone cyst is often asymptomatic but can cause pathological fracture. Aim of the study: The aim of our study was to evaluate clinical, diagnostic and treatment factors concerning patients with simple bone cyst. Material and methods: The retrospective analysis was performed on 22 patients treated in Department of Traumatology, Orthopaedics and Hand Surgery in Poznań between 2001 and 2017. We have analyzed epidemiological factors: age and sex; symptoms; clinical examination: range of motion, deformation and pain; X-ray: localisation, cyst index of Kaelin and MacEwan and presence of pathological fractures; treatment: methods, number of hospitalizations and effectiveness. Results: Mean age of patients was 10,8. From 22 patients 11 were females. Generally bone cyst was diagnosed because of pathological fracture - 18 patients (85,7%). Other reasons of X-ray diagnostic were: pain - 2 patients (9,1%), deformity - 1 patient (4,5%), incidentally - 2 patients (9,1%). The bone cyst was localized in humerus - 21 patients (95,5%), radius - 1 patient (4,5%). Treatment methods were various: 7 patients (31,8%) - Depomedrol injections, 4 patients (18,1%) - marrow injections, 4 patients (18,1%) - marrow and Depomedrol injections, 5 patients (22,7%) - injections with additional bone grafts, 3 patients (13,6%) - only bone grafts. Conclusion: Simple bone cyst occurs generally in young people (under twenty). The most common problem was pathological fracture.