The song describes an individual who feels tortured by society, and decides to "run away." It is one of the few songs on Hybrid Theory to contain unusually little rapping by Mike Shinoda, like "Crawling."
During live performances, two constant changes occur. Firstly, drummer Rob Bourdon performs a snare roll just before the second verse. Finally, during the second verse vocalist Chester Bennington alters the line "guilty by association" to "you're all guilty by association" while waving his arm to the audience. Both can be evidenced on "Live in Texas" and "The Family Values 2001 Tour" CD's. Runaway was a staple in live performances even before Hybrid Theory and was omitted in 2006 until the first leg of the Living Things Tour in 2012.
David Fricke of Rolling Stone noted the "tumbling funk" of Bourdon in the song, as well as the way that Shinoda and Bennington "shoot and share rhymes ... their bodies rocking with spasms of conviction." Writing of Linkin Park's remixing of the track for their album Reanimation, David Browne of Entertainment Weekly called "Rnw@y" "more sonically expansive" than the original version had been. He wrote that "Rnw@y" (along with a few others on the album) made Linkin Park sound like "experimental DJs."