This article reviews the major indications for chest sonography in children. Sonography should be performed after chest radiographs have been obtained in order to assess the need for further imaging with CT and/or MRI. Sonography allows accurate assessment of the pleural compartment especially for evaluation of pleural effusions, the diaphragm, peripheral lung lesions and anterior, middle and postero-inferior mediastinal lesions. Imaging of the thymus is emphasized because normal thymus can mimic pathologic situations and tumors may arise within the thymus. This technique allows tissue characterization and it is superior to other modalities in characterization of fluid. Sonography may be used to guide aspirations and biopsies. Sonography of the chest is the modality of choice in children because of its lack of ionizing radiation and ease to perform.