The authors report the cases of two children who presented in the first months of life with progressive macrocrania related to chronic pericerebral fluid collection. This condition resolved spontaneously without treatment after a few months in the first case, whereas it required several aspirations of blood-stained fluid via the fontanel in the second case. Both patients developed normally without evidence of disease in the earliest years of life and presented at the ages of 3 1/2 and 4 1/2 years, respectively, with symptoms and signs of rapidly progressing intracranial hypertension. In both cases contrast-enhanced computerized tomography and magnetic resonance imaging revealed masses in the subdural space of the skull base and the cranial vault associated with significant subdural fluid collections. In the first case the lesion was misdiagnosed in the initial phase and treated, by means of multiple craniotomies, as an organized subdural hematoma. After a diagnosis of liposarcoma had been made, the patient was treated with chemotherapy, which resulted in a good resolution of the lesions at 3-month follow-up review. In the second case a biopsy allowed the diagnosis of fibrohistiocytic sarcoma and the patient was treated with chemotherapy. The authors review the literature of the few reported cases and discuss the possible pathophysiological association between pericerebral fluid collection and the subsequent development of a subdural sarcoma.