A pulmonary pseudocyst is defined as a cyst that lacks respiratory epithelial cells. Lung pseudocysts are rare lesions in children and their classification is usually combined with other parenchymal cystic lesions. The distinction between a pseudo and a true cyst is difficult to distinguish both in utero and postnatally and can only be achieved on histology. Radiological investigations such as x-ray and computed tomography are equally non-specific. Most literature focuses on pseudocysts in adults particularly following blunt or penetrating chest trauma. In this report, we narrate a case of a lung pseudocyst initially misdiagnosed as a congenital lobar over-inflation in a child who presented with progressive shortness of breath and failure to thrive