The lack of registration of ultrasound contrast agents for use in patients below the age of 18 is a significant limitation of their usage. Despite this, examinations with the use of contrast agents are conducted in numerous centers, mainly as part of the diagnostic process of vesicoureteral reflux. Examinations after an intravenous administration of contrast agents are conducted rarely. The reason for this is not only the lack of registration, but also the lack of studies on their safety profile in paediatric patients or no guidelines concerning the dosage. It seems that imaging with the use of such agents could help solve certain clinical problems when other diagnostic methods fail. The paper presents selected cases of pediatric patients treated in oncological departments, in whom the examination with the use of ultrasound contrast agents had a considerable influence on the diagnostic and therapeutic process.