Background: Codeine misuse and dependence poses a clinical and public health challenge. However, little is known about dependence and treatment needs in the UK and Ireland. Aim: To characterize codeine use, dependence and help-seeking behaviour. Design: An online cross-sectional survey advertised on Facebook, Twitter, health and drug websites and e-mail circulars. Methods: The survey collected data on demographics and codeine use amongst adults from the UK and Ireland. The Severity of Dependence Scale measured the level of codeine dependence. Results: The sample of 316 respondents had a mean age of 35.3 years (SD=12.3) and 67% were women. Of the 316 respondents, 54 scored ≥ 5 on the Severity of Dependence Scale indicating codeine dependence (17.1%). Our study found that codeine dependence is a problemwith both prescribed and 'over-the-counter' codeine. Codeine dependence was associated with daily use of codeine, faking or exaggerating symptoms to get a prescription for codeine and 'pharmacy shopping' (P < 0.01). A higher number of respondents had sought advice on the Internet (12%) rather than from their general medical practitioner (GP) (5.4%). Less than 1% of respondents had sought advice from a pharmacist. Conclusions: Codeine dependent users were more likely to seek help on the Internet to control their use of codeine than from a GP, which may indicate a potential for greater specialized addiction treatment demand through increased identification and referrals in primary care.