Who Do You Think You Are is an uptempo dance-pop song, with influences of the early '90s europop, and a disco–style beat that resembles the music of the late '70s.It is written in the key of F♯ minor, with a time signature set on common time, and moves at a fast tempo of 120 beats per minute.
The song is constructed in a verse-pre-chorus-chorus form, with a bridge before the third and final chorus. It starts with an instrumental introduction, with a simple chord progression of F♯m7–G♯m7, that is also used during the verses. In the first verse, Geri Halliwell and Emma Bunton trade lines in a wry manner, then the chord progression changes to G7–Bm–G7–Bm–G7–F♯m7during the pre-chorus, which features Melanie Chisholm's vocals prominently. After the chorus, the same pattern occurs leading to the second chorus, with Victoria Adams and Melanie Brown singing the second verse. Then the group sings the bridge, the pre-chorus, and repeats the chorus until the song gradually fades out, while Chisholm adds the high harmony—"Swing it, shake it, move it, make it".
The inspiration for the lyrics comes from some of the people the group met in the music industry, and are about the presumptuous superstar life, and how someone can get trapped in the world of fame, much like the Temptations' 1971 classic Superstar (Remember How You Got Where You Are).