Arachnoid cysts are intra-arachnoid collections of cerebrospinal fluid. They may cause neurological deficit through expansion that can compress normal neural tissue and obstruct cerebrospinal fluid flow. Intracranial arachnoid cysts were found in 4 patients aged 10 months to 20 months(mean age 15 months). The presenting symptoms included circling(dog 2,3), seizure(dog 1), progressive weakness(dog 1,2,3), increasing scoliosis(dog 3), worsening spasticity(dog 3), and salivation(dog 3). One patient showed no symptoms from the intracranial arachnoid cyst. There were no significant findings in complete blood count and serum chemistry. Computed tomography(CT) with/without magnetic resonance imaging(MRI) scans were performed in these cases. Hypodense intracranial arachnoid cyst was observed on CT images in dog 4. Sagittal T1-weighted(T1W) and T2-weighted(T2W) images and transverse T1W and T2W images revealed a intracranial arachnoid cysts with syringohydromyelia(dog 3) and hydrocephalus(dog 3,4) in the brain. Clinical signs of three cases were improved by medication.