Aims To quantify tobacco and alcohol content, including branding, in popular contemporary YouTube music videos;and measure adolescent exposure to such content. Design Ten-second interval content analysis of alcohol, tobacco orelectronic cigarette imagery in all UK Top 40 YouTube music videos during a 12-week period in 2013/14; on-line nationalsurvey of adolescent viewing of the 32 most popular high-content videos. Setting Great Britain. Participants A tota lof 2068 adolescents aged 11–18 years who completed an on-line survey. Measurements Occurrence of alcohol, tobaccoand electronic cigarette use, implied use, paraphernalia or branding in music videos and proportions and estimated num-bers of adolescents who had watched sampled videos. Findings Alcohol imagery appeared in 45% [95% conﬁdence in-terval (CI) = 33–51%] of all videos, tobacco in 22% (95% CI = 13–27%) and electronic cigarettes in 2% (95% CI = 0–4%).Alcohol branding appeared in 7% (95% CI = 2–11%) of videos, tobacco branding in 4% (95% CI = 0–7%) and electroniccigarettes in 1% (95% CI = 0–3%). The most frequently observed alcohol, tobacco and electronic cigarette brands were,respectively, Absolut Tune, Marlboro and E-Lites. At least one of the 32 most popular music videos containing alcoholor tobacco content had been seen by 81% (95% CI = 79%, 83%) of adolescents surveyed, and of these 87% (95%CI = 85%, 89%) had re-watched at least one video. The average number of videos seen was 7.1 (95% CI = 6.8, 7.4). Girlswere more likely to watch and also re-watch the videos than boys, P < 0.001. Conclusions Popular YouTube musicvideos watched by a large number of British adolescents, particularly girls, include signiﬁcant tobacco and alcohol content,including branding.