Pneumoblastoma is a rare but severely aggressive primary lung tumor. Exceptional at the pediatric age, pneumoblastoma lacks clinical and radiological specificity. It is rarely mentioned as a first-line differential, as radiological images are often confused with those of congenital lung malformation. This history is reminiscent of the diagnostic difficulty with which the clinician is confronted with the finding of an intrathoracic cystic image of the child. Primary childhood lung tumors, especially pneumoblastoma, are difficult to diagnose both clinically and by imaging. It is necessary to think about it in the face of any lingering respiratory infection and any atypical radiological presentation. We report this case in order to illustrate the usual radiographic, ultrasound, and scenographic aspects of this rare malignant tumor in children and to highlight the diagnostic problems posed by this exceptional pathology.