Adolescents are a vulnerable population, not only to the acquisition of HIV, but also to poor adherence to antiretroviral therapy (ART) associated with disease progression and a increased risk of onward viral transmission. The aim of the study was to examine the factors that aid or act as barriers to adherence in a UK population of adolescents and young adults receiving ART. A cross-sectional survey was completed of 138 adolescents (12-24 years) across 14 clinical and community sites in the UK and Ireland. Analysis of results was undertaken using Chi-square testing in SPSS. Of the 138 patients, 48% were female, and 52% were born outside of the UK. Fifty-two of the 138 (43%) reported being on ART for at least 8 years. More than a third of the patients have ever interrupted treatment since initiating ART. One hundred four of the 138 (75%) patients self-reported being >85% adherent to medication for 7 day recall. Self-motivation (e.g., having a routine, specific goal) was cited as being most helpful in medication compliance (33%), followed by reminders by friends and family (25%), with 20% identifing no specific factor. Only 15% chose interventions such as an adherence diary or mobile phone reminders as helpful factors, and 1% chose healthcare professional input such as home visits. This study highlights the importance of self-motivation and social support in medication adherence in an HIV-infected adolescent population, in preference to healthcare professional input. Education and motivational strategies may confer the biggest impact on sustained ART adherence amongst this vulnerable group.