The Hidden Mansion mode in the European version was heavily altered and is much harder to complete compared to the Japanese and North American versions:
• Everything is mirrored from left to right.
• The mansion is much darker compared to the main game.
• Some of the ghosts that normally appear later in the game appear earlier.
• Boos have more health and are more difficult to be sucked up by the Poltergust.
• Chauncey's rocking horses are harder to avoid, since they are larger, zig-zag towards Luigi, and travel faster than in the normal mansion.
• In the Bogmire battle, there is time to capture him before he disappears.
• During the Boolossus battle, there is a small cutscene where Luigi must hop on the Poltergust and ride around on it while trying to pop him, making Luigi harder to control.
• In the King Boo & Bowser battle, Bowser's bombs have a shorter fuse.