The diagnosis of soft tissue masses in children can be challenging because there is a broad spectrum of entities that can present as such. Ultrasonography is the primary diagnostic imaging modality in the pediatric age and is especially useful for small and superficial lesions. MR imaging can be helpful, particularly in the evaluation of large and deep soft tissue lesions. Correlation of the imaging findings with the clinical information is crucial in the diagnostic work-up. This article reviews the most common causes of soft tissue masses that require imaging in children.