Arachnoid cysts are the benign developmental malformations of arachnoid compromising of about 1 % of all intracranial space occupying lesions. It was reported that trauma, also, might play a role in the pathogenesis of these lesions. These cysts are frequently seen in early childhood and have a tendency to middle fossa. These cysts frequently present with headache, dizziness, or epilepsy and suboptimal cerebral function like disordered perception. Natural course and treatment of these cysts are still in debate. In this report, we are presenting a 10 month year old child having symptomatic huge arachnoid cysts in middle fossa determined incidentally after trauma. In the treatment of this case, cystoperitoneal shunt operation was performed and good result was gained even in the early postoperative period. However, the main topic of this report is to emphasize that sometimes symptomatic cases might be overlooked.