Almost £50m of tickets have been bought by people seeing Harry Potter in the UK, but Lord of the Rings may sell even more.
Three films cost more than £200m
Experts on cinema think The Fellowship of the Ring, which is nearly three hours long, will sell more tickets around the world.
The three films in the Rings trilogy were all filmed in one go in New Zealand and cost more than £200m.
The other two will be released in 2002 and 2003.03.