CSF is not present in

Ventricle

Subarachnoid

Subdural

Spinal cord

The cerebrospinal fluidoccupies thesubarachnoid space(between thearachnoid materand thepia mater) and theventricular systemaround and inside the brain and spinal cord. It fills theventriclesof the brain as well as thecentral canalof the spinal cord.

So it is not present in subdural space. Note that subdural space is that space which can get opened if arachnoid and dura mater separate due to injury.