Cerebral hydatid cysts account for 2% of all intracranial masses. Preo
perative diagnosis is important since cyst rupture and spillage may ca
use an anaphylactic reaction. CT is the primary modality for the diagn
osis. Two forms of cerebral hydatid cysts have been reported on the ba
sis of CT appearances: unilocular and multilocular. Demonstration of t
he cyst wall is important for the diagnosis. MRI is superior to CT for
demonstrating the cyst capsule and perifocal oedema. We retrospective
ly reviewed the CT and MRI findings of 6 surgically proven cases of ce
rebral hydatid cyst and compared the two modalities on the basis of th
eir demonstration of findings helpful in the diagnosis, such as the ca
psule and perifocal oedema. In 1 case CT showed the capsule. In 2 case
s MRI showed a hypointense capsule around the cyst on T2-weighted imag
es. While CT is the modality of choice, in clinical practice MRI is su
perior for demonstrating the cyst capsule, which is a helpful finding
in the diagnosis and can be used in inconclusive cases.