"Hidden Treasures" is a collection of previously released non-album tracks, including soundtrack and compilation songs. The American version of the album is currently out of print, but the Japanese version is still available as of 2006. It was originally released in Europe as a special bonus CD for Youthanasia, before being released in Japan and the US as a separate EP later that year. A remastered version was released in Europe on April 30, 2007. The album debuted at #90 on U.S. Billboard charts.