Soft tissue malignancies are uncommon in adults and even rarer in children. Twelve children presented to the radiology department over a three-year period with a clinical diagnosis of a malignant lower limb mass. This diagnosis was usually based on the presence of a firm, painless mass. However, imaging revealed a heterogeneous group of benign pathologies: haemangioma (two cases), haematoma (two cases), aneurysm (two cases), and one case each of infection, myositis ossificans, Baker's cyst, lipoma, muscle rupture, and venous malformation. During the same period there was only one malignant soft tissue neoplasm. A variety of imaging techniques were used but ultrasound combined with colour flow Doppler was the single most helpful modality. The radiological diagnosis were confirmed by biopsy, surgery or clinical follow-up.