Now That's What I Call Music! 18 was released on March 15, 2005. The album is the eighteenth edition of the (U.S.) Now series. It peaked at number 4 on the Billboard 200 and has been certified 2x Platinum by the RIAA. The compilation includes one song which reached the Billboard Hot 100: "Drop It Like It's Hot".
The cover is inspired by the NOW 44 UK cover released in 1999.