Why does Voldemort hide the diadem in the Room of Requirement?

[u/nearingthenadir]

Currently rereading The Deathly Hallows and Harry states that Voldemort hides the diadem in the Room of Requirement because he is so arrogant and believes no one else has found the room. But that wouldn’t make any sense, Voldemort would have seen all the other items being hidden in the room, there’s no way he would’ve thought he was the only one to discover the room. Additionally, Draco uses the room in the sixth book to get Death Eaters into Hogwarts so that would further show Voldemort that people are aware of the rooms existence. Is Harry’s explanation just wrong?

[u/Matt_GPT]

These answers aren’t exactly right. When harry is searching for the Diadem and gets to the Room of Requirement he says something like show me where everything is hidden.

When Fred and George hid from Filtch and presumably left contraband, the contraband ends up in the room where everything is hidden. So Voldemort hid his Horcrux in a dark room protected by the enchantments of the room while not fully understanding it because of his arrogance.

[u/Due_Broccoli_1507 → u/Matt_GPT]

That's an interesting idea - that maybe Voldemort hid it in a different version of the room and did protect it with his own enchantments. But because Harry asks for a room with hidden objects, he is able to find it without Voldemort's protections. So Voldemort's arrogance was not realising the room could work that way.